physics refraction

REFRACTION- Waves changing direction at a boundry.

• when a wave crossses a boundry of a different material it
• if the wave hits the boundry of an angle- its refracted.
• The wave towards the normal if it slows down, it bends away from the normal if it speeds up.
• .How much it is refracted depends on the density of the two materials (usually the material with the highest density, the slower the wave travels through it)
• The wavelenth of a wave changes when it is refracted, but the frequency stays the same.

 Ray diagrams show the path of a wave.

• Rays are straightlines that are perpendicular to wave fronts. They show the direction of a  wave is travelling in. You can construct a ray diagram for a refracted light ray.
• The angle between the incident ray and the normal is the angle of incedence - always use a protacter when drawing the angle.
• The angle of refraction is the angle between the refracted angle and the normal.

All waves can ABOSRBED,TRANSMITTED OR REFLECTED.

When a wave meets a boundary between Two materials three things can happen.

• Absorbed- the wave is absorbed by the secound material- the waves transfer energy to the materials energy stores. The engery can tern into a thermal energy store, which could lead to it heating .e.g. microwave.
• Transmitted- the wave carries on travelling through the secound material which could lead to a change of speed, this often leads to refraction.
• Reflected- The wave is reflected this is wheere the incoming ray id neither absorbed or transmitted, but get 'sent back' away from the secound material. This is how echeos are created.

Continuous spectrem of EM waves.

• Electromagnetic waves are transferse waves.
• They transer energy froma source to an absorber.

E.G. A came fire transfers energy to its surroundings by emmitiing infared radiation. These infrared waves are absorbed by the objects and transfer to the objects thermel energy stor, causeing the object to warm up.

• All em waves travel the same speed through the air or the vacume (space). EM waves arent vibrations of partiicles but vibrations of electric and magnetic waves feilds. This means they can travel through space.
• They travel in different speeds in different materials, which can lead to refraction.
• We group them by there wavelenths and frequency. There are 7 groups, radio waves, micro waves, infra red, visable light,ultra violet, x-rays and gamma rays.
• Our eyes can only detect a small part of this spectrom- visible light.

Microwaves:

• communication to and from satalites, creating signal for thingslike TV and phones.
• For satalite TV the signal from the transmitter is transmitted through space ....  The satalite transmits the signal back to earth in a different direction.
• They have a long wavelenth and a low frequency.

Infra- red:

• infrared radiation is given out by all objects and the hotter the object, the more IR radiation it gives out.
• Infrared cameras can be used to detect infrared radiation and montinor temprecture.
• Aborbing IR radiation causes objects to get hotter.
• Food can be cooked using IR radiation E.G. toast in a toaster.
• Electric heaters heat a room in the same way, a long peice of wire in a heater heats up when a current flows through it (also glows-visable light). The thermel energy is absorbed by the objects in the room causeing the temoreture to increase.