physics: refraction

what is refraction

the bending or change in direction of light when it travels from one medium to another

what are the rules of refraction

• angle of refraction: the angle between the refracted ray and the normal

• the incident ray, refracted ray, and normal all lie on the same plane

• The incident ray and refracted ray are on opposite sides of the line that separates the two media

if speed of light in the second medium is slower than it was in the first medium what way does light bend

light bends towards the normal when the speed of light is slower than it was in the first medium

*angle of refraction is always smaller than the angle of incidence

if speed of light in the second medium is faster what way does light bend

light bends away from the normal if the second medium is faster

*angle of refraction is always larger than the angle of incidence

what’s the relationship between refraction/speed of light

the larger the index of reflection, the slower the light travels

what is total internal reflection

If the angle of incidence is increased past the critical angle, the refracted ray will bounce back to the medium. The ray of no longer considered refracted and is now reflected

for total internal reflection to occur:

• no light enters 2nd medium

• follows laws of reflection

Total internal reflection possibilities

• if the angle of incidence is small, the light refracts out

• at the critical angle, it refracts 90° along the boundary

• if the angle of incidence is greater than the critical angle, total internal reflection occurs

common uses of total internal reflection

• optical fibres

• binoculars

• diamond sparkle

• periscopes

phenomena of rainbows

• refraction: sunlight enters a raindrop and bends (white light splits into colours because each wavelength bends differently

• total internal reflection: the light bounces inside the raindrop

• refraction again: the light exits the drop, bending a second time

phenomena of mirages

• happens because speed of light is faster in hot air than cold air because index of refraction of air decreases as temperature increases

• the light ray travels up from the hottest layer to the cooler layer above and gradually refracted towards the normal as temperature increases

• at a certain angle, light undergoes total internal reflection and curves upward to your eyes

phenomena of apparent depth

• depth of an object appears to be at due to the refraction of light in a transparent medium

• light travels slower in water than air

• as light rays come out of the water into air, they bend away from the normal (refraction)

• your eyes trace the rays back in a straight line, making the object appear more shallow than it actually is