Unit 3 - Lenses

Question 1

What is refraction

Answer 1

When a ray of light crosses the boundry between two different transparent materials and it changes direction

Question 2

What does it mean hen something has deviated?

Answer 2

It has changed direction

Question 3

When light goes from air into a denser material, does it go towards or away from the normal? (when the wave slows down)

Answer 3

Towards

Question 4

What is the ray called that goes into the material?

Answer 4

The incident ray

Question 5

What is the ray of light called that has changed direction and is inside the material?

Answer 5

The refracted ray

Question 6

What is the ray of light called that goes out of the material?

Answer 6

The emergent ray

Question 7

When a ray of light goes from a denser material to an less dense material, does it go towards or away from the normal?

Answer 7

Away from

Question 8

What is the reason for the change in direction during refraction?

Answer 8

The change in speed

Question 9

At what angle is light not refracted?

Answer 9

90°

Question 10

What is the angle of incidence

Answer 10

The angle at which the ray of light hits the medium

Question 11

What the the refractive index fo a material?

Answer 11

the ratio of speed of light in a vacuum to speed of light in that medium

Question 12

What is the equation for the refractive index?

Answer 12

Refractive index = sin i / sin r

• I to the sky (outside the shape)
• R will always be smaller than r

Question 13

When given the angles of incidence/refraction, how do you encorperate this into the equation for the refractive index?

Answer 13

Do sin of the angle, and then use this in the actual equation (aka sin i / sin r)

eg I = 42° R=35°

sin i = sin(42)=0.67 and sin r = sin(35) = 0.57

So RI = 0.67/0.57 = answer

Question 14

The refractive index will always be..?

Answer 14

More than 1

Question 15

When working out the angle of refraction, what is the equation?

Answer 15

Sin i / n = sin r

→ Sin-1(ans) = answer

Question 16

How do lenses form images?

Answer 16

By refracting lights and changing its direction

Question 17

What are the two main types of lenses?

Answer 17

Converging and diverging

Question 18

Is a converging lense convex or concave?

Answer 18

Convex

Question 19

What is a convex lense and hat does it do?

Answer 19

A lense that buldges outwards and causes parallel rays of light to converge (move together) at the pricipal focus

Question 20

Is a diverging lenses convex or concave?

Answer 20

Concave

Question 21

What shape is a concave length? and what does it do

Answer 21

It caves inwards, it causes parallel rays to diverge (spread out)

Question 22

What is the axis of a lens?

Answer 22

A line passing through the middle of the lens

Question 23

What is the principal focus.focal point of a converging lens?

Answer 23

Where rays hitting the lens parallel to the axis all meet

Question 24

What is the principal focus/focal point of a diverging lens?

Answer 24

The point where rays hitting the lens parallel to the axis appear

Question 25

What is the focal length

Answer 25

The distance from the centre of the lens to the principal focus/focal point