11.3/8 Reflection and refraction/refractive index

Question 1

What is reflection?

Answer 1

Reflection occurs when a wave changes direction at a boundary between two different media, remaining in the original medium.

Question 2

What is the law of reflection?

Answer 2

angle of incidence = angle of reflection (all angles are measured from the normal line or the line perpendicular to the surface)

Question 3

What is a wavefront?

Answer 3

A wavefront is a line joining points on a wave that are in phase.

Question 4

What is refraction?

Answer 4

Refraction occurs when a wave changes direction as it
changes speed when it passes from one medium to another; if the new medium is:
-optically denser than the original medium, the wave will refract towards the normal and slow down.
-less optically dense than the original medium, the wave will refract away from the normal and speed up.
The amount of refraction depends on the refractive index of the material.

Question 5

What is Snell’s Law?

Answer 5

n1 x sinθ1 = n2 x sinθ2
where:
-n1 is the refractive index of the original medium
-sinθ1 is the incident angle
-n2 is the refractive index of the new medium
-sinθ2 is the refracted angle

Question 6

What effect does reflection and refraction have on wavelength?

Answer 6

Reflection does not have any effect on the wavelength of a wave. Refraction does however; if the wave slows down, its wavelength decreases and vice versa. Frequency remains constant during this effect.

Question 7

What do you think will happen when a water wave enters shallow water?

Answer 7

-As the water depth decreases the wavelength decreases therefore wavespeed decreases.
-As the wavefront approaches shallow water at an angle, the part of the wavefront in shallower water slows down more than the part in deeper water. This causes the wavefront to bend or refract, aligning more parallel to the coastline.

Question 8

How is the refractive index of a material calculated?

Answer 8

n = c / v
where:
-n is the refractive index
-c is the speed of light in a vacuum (3.00 x 10^8 ms^-1)
-v is the speed of light in the material

Question 9

What is the relationship between refractive index and refracted angle?

Answer 9

Directly proportional - the greater the refractive index is, more light entering the material is refracted towards the normal.

Question 10

What is the refraction law?

Answer 10

n sinθ = k
n = sinθ1 / sinθ2