Some questions about light

Please only reply if you know a lot about physics, because I need reliable answers.

I have a few questions and would be very grateful if you could answer them, hopefully to GCSE standard.

Why does a light interference pattern suggest that light is transverse?

How would you use simple mathematics to work out that electromagnetic waves travel at the speed of light?

How would you show that light is an electromagnetic wave?

Reply 1

teachercol

1) It doesnt. Longitudinal waves show interference patterns too. Polarisiation shos light is transverse.

2) No idea - you can derive the speed of light from Maxwell's equations but not using 'simple' maths.

3) They can travel through a vacuum.

Reply 2

joeahuja

well for number two assuming the distance from the sun to the earth is known and you somehow manage to find out how long light takes to get from the sun to earth then you can use v=d/t

lol but i know in order to find out the distance of the sun from the earth and the time takes for the light to travel the speed of light must already be known but to GCSE standards these values might be given. Hope this helps :smile:

Reply 3

mipegg

Why does a light interference pattern suggest that light is transverse?

Well it doesnt per say. Interference patterns are created whenever you diffract a wave, though you can diffract longitudinal as well as transverse waves. Surely polarization would show it was transverse?

How would you use simple mathematics to work out that electromagnetic waves travel at the speed of light?

Distance=Speed*time
Speed=Distance/Time

Simple experiment, use a light of some description, turn it on over a given distance and measure how long it takes to get there

How would you show that light is an electromagnetic wave?

Check it has the qualities that electromagnetic waves do

Travel through a vacuum (at 3*10^8)
Is transverse->can be polarised
Has a magnetic field at 90 degree orientation from the wave