Caractéristiques d’une onde plane:

Si on se trouve dans une zone située assez loin de l’antenne, les champs E et B ont des propriétés simples :

  • le vecteur E a le même module en tout point d’un plan perpendiculaire à la propagation, E et B sont liés par :

E= C . B

  • le vecteur E est perpendiculaire à B, l’onde est dite plane.
  • les 2 vecteurs E et B sont perpendiculaires à la direction de propagation.
  • E et B varient en phase, les plans où E et B sont maximum avancent à la vitesse c de la lumière vecteur

 

 

 

Remarque: la direction du brin rayonnant correspond à celle du champ électrique et est appelée polarisation. Avec l’antenne verticale de la figure ci-dessus, la polarisation est verticale.

Call of Duty Modern Warfare 2

As one of the most critically acclaimed shooters of all time, Call of Duty 4: Modern Warfare is a prime example of a tough act to follow. Yet, amidst a raging storm of anticipation and expectation, Call of Duty: Modern Warfare 2 has done it. The new campaign is chock-full of intense action and dramatic moments, and though it is more muddled than its predecessor (in more ways than one), it’s still an absolute blast. The new Special Ops mode allows you to experience some campaign-inspired thrills with a friend and it’s an engaging challenge to coordinate your maneuvers and tackle the varied objectives. Last but not least, the competitive multiplayer that took the online shooter community by storm two years ago is back. Though the addictive action remains the same at its core, there are a host of new elements that make matches more accessible, more strategic, and more rewarding. Unfortunately, these improvements are marred by limited online flexibility that may leave the PC shooter community out in the cold.

The campaign takes you to some dangerous, claustrophobic places.
The campaign takes you to some dangerous, claustrophobic places.

If you compare Modern Warfare 2 on the PC to its console counterparts, the game is every bit as awesome and enjoyable. Yet when compared to other online shooters on the PC, the multiplayer component is decidedly limited. Players cannot set up dedicated servers to host their own custom-tuned matches, and the player count for each match has been capped at 18 as opposed to the possible 64-player matches of Call of Duty 4: Modern Warfare. Furthermore, there is no support for user-created content, so rather than enjoying free mods and community maps, PC users will have to pay for downloadable content. And the money issues don’t stop there: Modern Warfare 2 costs $10 more than most full-price PC games. Paying more and getting less is abhorrent to consumers, and this deterrent, along with the online restrictions, make Modern Warfare 2 much less appealing from a multiplayer perspective. Yet despite this disappointment, there is still a lot to love about the online multiplayer, and the other elements of the game remain unblemished.

The campaign picks up where its predecessor left off, and there’s a new violent ultranationalist terrorist on the scene. Once again, you play as a few different soldiers who are part of the effort to make the world a safer place. Your missions take you around the world to a number of exotic locations and engage you in a variety of different conflicts, ranging from stealthy and silenced to crowded and cacophonous. The action is smooth and exhilarating, thanks to sharp shooting and movement mechanics that allow you to be as quick and deadly as your skills permit. Environments are well designed and detailed, though many textures don’t look particularly good upon close inspection. Modern Warfare 2 isn’t a beautiful game, but it looks great in action. The diverse levels not only provide varied sights, but they are also cleverly designed to allow the action to flow at an exciting pace. Opportunities for cover and flanking present themselves naturally, allowing you to move through the battlefield in a variety of fluid ways. The aggressive enemy AI will keep you on your toes, and achieving your hard-earned success is satisfying.

Modern Warfare 2’s campaign, like that of its predecessor, is quite short, and you’ll likely finish it in about five hours. Though it is disappointing that there isn’t more of it, what you do get is a relentless barrage of tight combat and thrilling set pieces. In one early level, you man the turret of a Humvee patrolling the claustrophobic streets of a Middle Eastern city. Enemies seem to be around every corner, but you are ordered not to fire until fired upon. The tension builds, and once you are engaged by the enemy, all hell breaks loose. After a hectic (and unsuccessful) flight from danger, you end up fighting door-to-door in the streets and ruined buildings. This frantic combat ratchets up when you head to the slums of Rio de Janeiro and reaches a whole new level when you find yourself engaged in similarly intense firefights on the grassy lawns and paved driveways of suburban America. The fight on the home front has some very cool moments, but it doesn’t mean you’re done adventuring abroad. A dramatic prison rescue, a marine infiltration, and a snowmobile chase are just some of the other exhilarating moments that make this campaign so enjoyable.

Downed military helicopters aren't exactly a boon for Nate's restaurant.
Downed military helicopters aren’t exactly a boon for Nate’s restaurant.

Though completing the campaign is an intensely satisfying and exciting endeavor, you may not feel very triumphant when all is said and done. Modern Warfare 2 features some dark plot turns, and your missions sometimes have drastic unintended consequences. In one mission in particular, you infiltrate a terrorist cell and are called upon to do the kind of things that terrorists do. What follows is a neutered attempt at portraying the grim reality of terrorism, and concessions are put in place to keep the plot from getting too dark. Despite these limits, the scene in question is undeniably disturbing and undermines your sense of remaining on high moral ground. The game gives you the option to skip this particular level entirely, but the shocking consequences of this grim mission ripple throughout the game, making it difficult to feel like a hero. Subsequent developments further muddle your overall objective, and it doesn’t help that many of the subtleties and connecting threads are mumbled during voice-overs between missions. The plot ends up being a bit disorienting, and you may get the feeling that, rather than being the tip of the spear, you are just along for the ride.

If you’re looking for some campaign-style action that is unburdened by any sort of plot, then Special Ops is the place to go. The timed missions are campaign excerpts from Modern Warfare 2 and Call of Duty 4: Modern Warfare that you can play solo or online with a friend. The missions cover a variety of objectives, which include surviving waves of enemies, moving from point A to point B stealthily (or not), eliminating a certain number of enemies, and racing snowmobiles. You earn a rating based on your completion time or difficulty level and unlock new missions as you progress. Though the missions will adjust to allow you to play solo, Special Ops missions are made to be played cooperatively. Two guns are better than one when clearing out a crowded slum full of enemy combatants, and coordinating a simultaneous sniper attack is much more fun when you are counting down with a buddy. There are also a few missions in which one player uses an airborne vehicle-mounted gun to clear the path for the other player on the ground, and these are frantic and explosively awesome. There is no matchmaking, however, so if you don’t have any friends online and need a teammate, you’ll have to go fishing in the multiplayer lobbies. As is the nature of cooperative play, missions can fall flat if teammates don’t communicate or go off on their own. It can be tough to find a communicative teammate who is willing to let one player take point, but it is certainly worth the effort. When you have a strong team assembled, cooperative play is uniquely fun, and Special Ops provides a great variety of engaging missions.

Of course, you could completely ignore both the campaign and cooperative modes and be very happy with Modern Warfare 2, despite the aforementioned online limitations. The insanely addictive, intensely exciting multiplayer formula pioneered by Call of Duty 4: Modern Warfare is in full effect here. The action is even faster and deadlier than the campaign, and killing enemies, accomplishing objectives, and completing challenges earn you experience points. These points increase your level and unlock new guns, new equipment, and new skill-boosting perks. You can design different classes to highlight different skills and then switch between them to adjust for the ebb and flow of battle. The core action remains largely the same, so folks who didn’t enjoy it the first time around aren’t likely to have a change of heart. And players who thrive on the diversity of dedicated servers and the creativity of mods and community maps will feel a keen sting of disappointment. Yet despite these omissions, Modern Warfare 2’s multiplayer action is so expertly balanced and riotously fun that it’s hard not to have a great time with it. And a number of new tweaks and additions make the action more engaging than its predecessor.

If the blood splatter bothers you, don't sweat it too much. You'll probably be dead soon.
If the blood splatter bothers you, don’t sweat it too much. You’ll probably be dead soon.

First off, weapon loadouts have been restructured. Guns you may have previously equipped as primary are now only available as secondary, so you can equip both an assault rifle and a shotgun if you so desire. This restructuring creates an intriguing array of gun combinations, and one of the new options isn’t even a gun. The bullet-resistant riot shield can be equipped in your primary slot and used to assault heavily contested positions. Having multiple-shielded teammates can change the battlefield significantly, and new equipment items deepen the strategic possibilities. The blast shield can protect you against grenade-happy opponents, while the tactical insertion flare (allows you to designate your next spawn point) can be a powerful asset in objective-based modes like Demolition and Domination.

The perk system has also received an overhaul. Perks can now be upgraded through use and will eventually grant a secondary ability. These bonus abilities are often just as potent as the primary perk, though they aren’t a linear extension of the primary ability. Upgrading the perk that grants increased melee distance, for example, will cause you to take no fall damage (allowing you to perfect your drop-and-stab maneuver). The new death streak perks may seem familiar to those acquainted with the infamous martyrdom perk from COD4, but they also provide some welcome (and cleverly implemented) aid for new players. These perks kick in after you die a few times in a row without getting a kill. Painkiller grants you increased health for a short time upon respawning and makes it easier to resist getting spawn killed. Copycat allows you to mimic the class of the last person that killed you, potentially granting you the guns, equipment, and perks of a much higher ranked opponent. Nothing mitigates the frustration of getting killed by a weapon you can’t access like getting your hands on that weapon and doing some killing of your own.

Customizable kill streak rewards are the other significant addition. In COD4, kill streaks of a certain length would earn you rewards like air strikes and attack helicopters. In Modern Warfare 2, there are a host of new rewards that you can unlock and then equip as you see fit. The rewards themselves range from tactical aids like unmanned aerial vehicles that reveal enemies on the radar (or counter UAVs that block the enemy’s radar) to powerful assaults like gunships, air strikes, and the exceedingly fun laptop-guided predator missile. Each kill streak requires a certain amount of kills to activate, and you can only equip three at a time, so there’s a risk/reward mechanic at play. The chopper gunner reward is superpowerful, but if you aren’t confident you can score the required 11 kill streak, you’ll essentially be wasting a reward slot. Even if you can’t string together 11 kills, you can still use some of the more powerful rewards courtesy of care packages. This reward drops a crate onto the battlefield that either contains an ammo resupply or a kill streak reward, such as a precision air strike. Not only do these rewards add an engaging strategic dimension, but they also do so in a way that allows all players to enjoy them.

In the slums of Rio, a scoped assault rifle is a man's best friend.
In the slums of Rio, a scoped assault rifle is a man’s best friend.

The result of all these multiplayer tweaks is a richer, more strategically nuanced experience and a busier battlefield. Fortunately, the action generally remains on the good side of hectic, and the stream of rewards is as satisfying as ever. Two new elements, title and emblem, are little graphics and titles that you earn through your match performance, ranging from serious to totally goofy. While not exactly in keeping with the serious tone of the campaign, they add an amusing way to further customize your online presence. Though it features a robust variety of playlists in which to ply your deadly trade, Modern Warfare 2’s competitive multiplayer is still limited compared to modern standards and will likely disappoint many hardcore shooter fans. The high price point sharpens the sting of these restrictions, but the core multiplayer action is still very addictive and very rewarding. The inelegant campaign plot may make you feel like you’re just along for the ride, but it is such an intense, roaringly great ride that you will be glad just to have played it. And the cooperative missions provide a uniquely fun angle on the action that rounds out the package superbly, making Modern Warfare 2 thoroughly entertaining and thoroughly rewarding.

Photos from Gamespot.com

Assassin’s Creed Black Flag

How far can you stray from home before it’s impossible to ever return? That’s the question at the heart of Assassin’s Creed IV: Black Flag. It’s something that plagues Edward Kenway, the game’s roguish hero, as he explores the Caribbean in search of wealth and the dream of returning to England a more respectable man. But for as much as Kenway longs for the day he can leave the pirate life behind, the freedom of the open sea is a difficult thing to resist. And who can blame him? Because after this stunning and beautifully realized tale of adventure on the high seas, it’s hard to imagine the Assassin’s Creed series returning to its landlocked roots

The world of Black Flag is nothing short of remarkable. This is the most expansive setting in the history of the franchise, a virtual rendition of the West Indies that encompasses all manner of burgeoning colonies, Mayan ruins, and deadly jungles. Cities like Havana and Nassau reflect the series’ trademark attention to detail, from the stonework cathedrals of the former to the ramshackle taverns of the latter. Then there are the remote islands inhabited by nothing more than crabs and sea turtles, underwater shipwrecks waiting to be explored, and vast stretches of sparkling Caribbean waters that are every bit as deadly as they are gorgeous.

Indeed, what makes Black Flag so special is the way it captures the thrill of sailing the open sea. It’s more than the spectacle of a humpback whale leaping into the air and spraying the deck of your ship, or the sound of your crew breaking out into a sea shanty just as the sun is beginning to set across the horizon. It’s the feeling that there’s always something out there to be discovered, rewards waiting to be captured no matter who’s standing in your way.

Simply sailing into the sunset is a delight in Assassin's Creed IV: Black Flag.
Simply sailing into the sunset is a delight in Assassin’s Creed IV: Black Flag.

What began as a series of isolated side missions in Assassin’s Creed III has exploded into a full-fledged means of exploration, discovery, and combat. Early into Black Flag, Kenway takes the helm of the Jackdaw, a pirate ship that has clearly seen better days. From there, it’s your charge to build the Jackdaw into a vessel capable of taking on the most powerful warships in the Caribbean. After all, that Spanish gold isn’t going to plunder itself.

Taking on naval superpowers seems like a tall order early on, but pushing yourself to improve your once-rickety ship is a process that Black Flag makes incredibly rewarding. This is a game that gives you an absurd number of ways to acquire the coin and resources needed to hold your own at sea. You might run off in search of buried treasure using nothing more than a crudely drawn map, or silently infiltrate a military storehouse to collect the wood and metal needed to bolster the Jackdaw’s hull. That bit of flotsam floating in the distance might be a crate of rum you can sell to make up the difference on your new mortar upgrades, or it might be a stranded sailor you can rescue to expand the size of your crew. Black Flag doesn’t just present a beautiful world; it gives you a mountain of reasons to run off and go exploring.

Black Flag builds on ACIII's naval side missions to create an experience every bit as important as running around on dry land.
Black Flag builds on ACIII’s naval side missions to create an experience every bit as important as running around on dry land.

Upgrading your ship is critical because Black Flag places a huge emphasis on naval combat. Both the storyline and side missions are full of tense sea battles, where strategic positioning and explosive cannon fire come together in exhilarating contests of naval supremacy. It’s a system that allows for a variety of tactics while never getting bogged down in overly complex controls, whether you’re picking off enemies from afar with a well-placed mortar strike or dumping explosive barrels into the path of an unsuspecting foe. Whatever approach you take, managing sea battles is an absolute blast.

It’s not just wanton mayhem, either. Black Flag encourages you to take pause and survey the landscape before charging into a fight. With the help of your spyglass, you can scout another ship’s cargo to decide whether the resources onboard match your current needs, as well as scout out how much money you’ll be able to loot. This same tool also reveals an enemy’s overall combat level, letting you know if you should warm up against a few more level-8 schooners before taking on that level-20 frigate. All this reconnaissance makes naval combat that much more satisfying; success comes not only from how accurately you lob your cannons, but from how adeptly you measure the risk versus the reward.

These naval battles often lead directly into more traditional Assassin’s Creed swordfighting, and it’s in those seamless transitions that Black Flag fuses its two halves into one cohesive whole. Destroying a ship outright rewards you with only half its cargo, so you need to board these vessels and wear down their reluctant crews to reap the full reward. That means swinging acrobatically from one ship to another, exchanging sword strikes with enemy sailors, and watching your crew erupt in cheers once those enemies have surrendered. A similar transition occurs during the game’s numerous fort takeover missions, where you bombard the defenses of a seaside fortress by ship before charging into the ensuing chaos to assassinate its officers amid a storm of fire and smoke.

That these acts of naval piracy continue to be so exciting so deep into the game’s lengthy story campaign is a testament to just how excellent Black Flag’s progression loop is. Raid an enemy gunboat, and you can scrap it for parts or send it on trade route missions to earn more money on the side. Overtake a fort, and you’ll unlock dozens of new activities on the map, whether they’re the location of great white sharks whose skin you can turn into improved armor or an underwater shipwreck you can explore once you’ve saved up enough for that diving bell. No matter where you go or what you do, it’s virtually impossible to feel like you’re not advancing in some way.

And it’s a quick game to advance, too. Assassin’s Creed III’s crawling preamble and frequent pacing issues are nowhere to be found here, as Black Flag wastes no time throwing you into the life of a pirate. The story revolves around the aforementioned Edward Kenway, a charming troublemaker from Bristol by way of Swansea. If his name sounds familiar, it should: Edward is the grandfather of ACIII protagonist Connor Kenway. The elder Kenway’s backstory is rooted in a fairly standard trope–a peasant off in search of wealth to build a better life back home–but it’s his unique place in the series’ overarching fiction, and the universal themes the story explores, that makes the narrative shine.

Storms have a way of catching you off guard in Black Flag.
Storms have a way of catching you off guard in Black Flag.

At the game’s outset, Kenway is neither assassin nor templar. He’s a man whose only allegiance lies with his ship’s crew, playing both factions against one another for his own gain. But as the years wear on, the luster of youthful indiscretion fades away as Kenway wrestles with a desire to find some greater purpose and a longing to do right by his estranged wife back home. It’s a story that explores the human side of pirates, painting larger-than-life figures in a light that even manages to turn Blackbeard into a sympathetic character.

The narrative grows a bit unwieldy toward the end, but finds its footing just before a credit sequence that is far more touching than any story about pirates has a right to be. An eclectic cast of side characters briefly dance with but never fully tackle more powerful themes like race and gender in the age of colonialism, but such narrative flirtations are one of the few shortcomings in an otherwise terrific story. Even the modern-day chapters–brief and innocuous as they may be–manage to add a refreshing and occasionally humorous take to the Abstergo story arc.

Despite the presence of pirates and scoundrels, the world of Black Flag is a consistently gorgeous one. The Assassin’s Creed series has always had a knack for establishing an engrossing sense of place in its dense urban landscapes, and Ubisoft hasn’t missed a step in applying that same level of craftsmanship toward the islands and jungles of the Caribbean. Black Flag looks especially impressive on the PlayStation 4, where improved lighting and a greater resolution bathe the world in a terrific level of visual fidelity and artistic flourishes. You’re better able to notice the little things, like the way foliage gives way to Kenway while he sneaks through the bushes, or the realistic flutter of fabric on your sails when a strong wind sweeps across the sea. The current-generation versions of Black Flag still look terrific, but all those little details in the PlayStation 4 version draw you into the world that much more.

Cities like Havana echo the classic environments of previous games.
Cities like Havana echo the classic environments of previous games.

Kenway’s adventures on dry land don’t amount to the same wholesale reinvention of the series that his time aboard the Jackdaw does, but these portions of the game have hardly been ignored. Ubisoft has borrowed a number of concepts from Far Cry 3, and they improve the on-foot experience immensely. Crafting animal hides into better equipment is a far greater incentive to hunt wild animals than it was in ACIII, while the ability to sabotage alarm bells in an enemy base adds more flexibility to the stealth experience. But once a fight breaks out into a full-on melee, Black Flag begins to feel much more like its predecessors: swordfighting is as fluid and lively as ever, but lacks any substantial refinements over previous games.

Where that sense of deja vu hits Black Flag the hardest is in its overuse of eavesdropping missions. Throughout the main story, the game asks you time and again to tail your targets (but not too closely!) and eavesdrop on their conversations (but not too obviously!) before finally letting you decide what to do with them. These types of missions–a staple of the very first game in the series–had already begun to show their age in recent Assassin’s Creed installments, and time hasn’t done them any favors since then.

Not all treasures are above water in Black Flag.
Not all treasures are above water in Black Flag.

While less glaring, a similar lack of advancement can be found in Black Flag’s multiplayer. The cat-and-mouse nature of Wanted and the co-op chaos of Wolfpack are still tremendous fun, but outside of a new story-driven tutorial mode, there aren’t any substantial additions. Even though Assassin’s Creed multiplayer has always occupied something of an « icing on the cake » role, it’s a shame this part of the game hasn’t enjoyed the same creative renewal that its single-player portion has.

But these moments of stagnation are isolated events in what is, ultimately, a massive and highly ambitious game. Black Flag presents a world full of adventure and opportunity, where treasures scavenged in a remote jungle can be used to turn the tide in a massive naval battle against mighty Spanish warships. It’s a game where you can sail the seas for hours at a time, either hunting great white sharks or simply listening to your crew sing one infectious sea shanty after the next. There’s an incredible scope to what you can do in Black Flag, with a level of harmony between its component parts that encourages you to try it all, and a story that keeps you invested throughout the whole thing. If there was ever any question that Assassin’s Creed needed something ambitious to get the series back on track, Black Flag is that game and then some.