Speed of light, laws of reflection and refraction
Answers are for parents and teachers.
1
At its closest, Mars is about 5.6·10⁷ km from the Earth. How long does a radio signal take to reach Mars (c = 3·10⁵ km/s)?
t ≈ 1.9·10² s, i.e. about 3 minutes
2
A person stands 1.5 m from a plane mirror and walks 0.5 m towards it. How far is the person from their image now?
1 m from the mirror, and the image is 1 m behind it: the distance is 2 m.
3
The speed of light in a medium is 2·10⁸ m/s. Find its refractive index.
n = 3·10⁸/(2·10⁸) = 1.5
4
A ray goes from air into glass (n = 1.5) at 30°. Find the sine of the angle of refraction.
sin β = 0.5/1.5 ≈ 0.33
5
Why does a rough wall not form a mirror image, yet we can see it from every side?
Light is reflected diffusely in all directions.