Prisms

Question 1

Prism?

Answer 1

Two flat polished refracting surfaces inclined at an angle relative to each other

Prisms have an apex, apex angle, base

Question 2

What does dispersion mean?

Answer 2

When a beam of light passes through a prism it splits into a spectrum of colours

Question 3

Why is blue light refracted more than red light?

Answer 3

Blue is shorter in wavelength

Question 4

Dispersion can not occur for what light?

Answer 4

Monochromatic light

Question 5

Where does the light move towards?

Answer 5

The base

Question 6

Where does the image move towards

Answer 6

The apex

Question 7

What is the angle of deviation dependant on

Answer 7

-refractive index of prism
-angle of incidence
-apex angle

Question 8

What is the angle of deviation

Answer 8

The light ray is deviated towards the base of the prism, this net change in direction is called the angle of deviation

Question 9

What is the minimum angle of deviation

Answer 9

It occurs when the light passes symmetrically through the prism, the angle of incidence equals the angle of emergence

Question 10

What are the unit for prisms

Answer 10

Prism dioptre
Centrad

Question 11

Where does displacement happen for a prism diaptore

Answer 11

Over a flat surface

Question 12

Displacement for centrad?

Answer 12

Over an arc

Question 13

Prism power?

Answer 13

How much the prism causes the light to change direction

Question 14

Prism dioptre formula

Answer 14

P= shift in cm/ distance in m

Question 15

Prisms at more powerful in what position?

Answer 15

Prentice position than in the position of minimum deviation

Question 16

Prentice position?

Answer 16

90 degrees to the interface and straight

Question 17

Using mostly thin prisms leads to?

Answer 17

Good quality images, this is shifted but not deformed because of the small apical angle of the prism

Small apical angle= good image quality

Question 18

What is a Lens

Answer 18

A lens is an optical device used to alter the vergence of light passing through it

Question 19

What is the formula for vergence power or surface power

Answer 19

F = n2-n1 /r

If F IS POSITIVE than it’s converging- moving towards axis
IF F IS NEGATIVE THAN it’s diverging

F IS MEASURED IN D (diopters) not that same as prims diopters

Question 20

How do you identify a convex lens

Answer 20

It’s thicker in the centre and thinner edge

Other forms of convex lenses are biconves lens, plano convex and convex meniscus which all have a positive vergence power

Question 21

How to you identify concave lenses

Answer 21

Thin centre and thicker edge

Examples are biconcave lens, plano concave and concave meniscus which all have a negative vergence power

Question 22

Thins Lens?

Answer 22

Thickness can be ignored so bending of light rays takes place approx at the centre of Lens

Question 23

How many focal points do lens have

Answer 23

2

Question 24

How many focal points do mirrors have

Answer 24

1

Question 25

For a convex lens where is F2 located

Answer 25

Behind the lens

Question 26

For a convex lens, where is F1 located

Answer 26

Infront of the lens

Question 27

For concave lens where is F2 located

Answer 27

Infront of the lens- this is where parallel rays cross

Question 28

For concave Lens where is F1 located

Answer 28

Behind the lens so rays from F1 are deflected into parallel rays

Question 29

What is the vergence power related to

Answer 29

The focal point

• the shorter the focal length the more powerful the lens

Question 30

The vergence power is related to the focal point
What is the formula to calculate the focal length?

Answer 30

F= 1/ f(in metres)