Total internal reflection and diffraction

Question 1

what is Snells law again

Answer 1

The ratio of the sine of the angle of incidence in one medium to thesine of the angle of refraction in the other medium is constant.

Question 2

what is the critical angle

Answer 2

Critical angleis the angle of incidence in the optically denser medium forwhich the angle of refraction in the optically less dense medium is 90°.

When calculating the critical angle, light is always travelling from a denser to a less dense medium and the angle of refraction is 90°.

Question 3

what happens when the angle of incidence exceeds the critical angle for the medium

Answer 3

a phenomenon calledtotal internal reflectiontakes place. For any angle of incidence larger than the critical angle, you can’t use Snell’s law to solve for the angle of refraction, because it will show that the refracted angle has a sine larger than 1, which is not possible.

Question 4

what are some conditions for total internal reflection

Answer 4

• The light ray moves from a more dense medium to a less dense medium.
• The angle of incidence must be greater than the critical angle.

Question 5

what is Huygens principle

Answer 5

Huygens’s principle states that every point of a wavefront serves as a point source of spherical, secondary waves that move forward with the same speed as the wave.

Question 6

Huygens principle explained

Answer 6

1. waves are made out of a series of points. These points all are a source of small circular secondary wavelets, which is simply a term for a small waves
2. each small wavelet will in turn produce a wavefront if you join the front of the wavelets with a line.
3. The new wavefront is drawn by drawing a tangent of all the new wavelets

Question 7

what are some limitations of Huygens principle

Answer 7

The principles of Huygens generally failed to explain the photoelectric effect