Lenses

Question 1

How can you tell if the light is slowing down?

Answer 1

If when it’s refracted, it bends towards the normal

Question 2

How can you tell if the light is speeding up?

Answer 2

If when it’s refracted, it bends away from the normal

Question 3

What is the normal?

Answer 3

A line that is perpendicular to the interface of the medium

Question 4

What is the refractive index?

Answer 4

A measure of how much the material slows down light

Question 5

What is the formula for the refractive index of a material?

Answer 5

n = c/v
refractive index = speed of light/ the speed of light in the material

Question 6

What does Snell’s law state about the refractive index of a material?

Answer 6

When light travels through an optically denser medium it is refracted toward the normal so
n1sin(angle of incidence) = n2sin(the refracted angle)

Question 7

What is the critical angle?

Answer 7

When light travels from a denser to a less dense medium,
there is an angle of incidence that causes the light to be refracted at 90 (on the boundary of the medium

Question 8

What is the formula used when the light goes from a material boundary to air?

Answer 8

sinC(critical angle) = 1/n (this is because n of air is 1 and the sin90 is 1)

Question 9

What are lenses?

Answer 9

Something that changes the direction of light using refraction

Question 10

What are converging lenses?

Answer 10

Lenses that bulge outwards and cause light to converge at the principal focus point

Question 11

In converging lenses what happens to rays that are parallel to the principal axes?

Answer 11

They are refracted until they converge at the principal focus point.

Question 12

What is the focal length?

Answer 12

Distance between the lens and the focal plane
Where parallel rays ( from infinity) are brought to a point.

Question 13

What are diverging lenses?

Answer 13

They cave inwards. The principal focus point is before the lens. So they cause the rays to spread out

Question 14

What is a real image?

Answer 14

Light rays that are actually there and can be captured on screen.

Light rays converge to a point where the image can be found.

Question 15

How is a real image formed?

Answer 15

When light rays from an object are made to pass through another point in space

Question 16

What are virtual images?

Answer 16

Light rays that aren’t actually there so cannot be captured on a screen

Question 17

How are virtual images formed?

Answer 17

When light rays on an object appear to have come from a different point in space

Question 18

What is the relationship between converging lenses, real images, virtual images, and the distance from the focal point?

Answer 18

If the object is closer to the lens than the focal point is, then it will form a virtual image

If the object is further away from the lense than the focal point then it will form a real image.

Question 19

What type of image will a diverging lens form?

Answer 19

Always a virtual image

Question 20

What is the formula that links the image length(v), the object length(u), and the focal length(f)?

Answer 20

1/f (Power of lens)= 1/u +1/v
Only works for thin lenses tho xD

Question 21

What is the formula for the power of a lens?

Answer 21

P = 1/focal length

Question 22

What are the units for the power of a lens?

Answer 22

Dioptres (D)

Question 23

What is the formula for magnification?

Answer 23

magnification = image height/ object height?
m = v/u

Question 24

How to find the critical angle between 2 media?

Answer 24

SinC = n²÷n¹

Question 25

What do “u” and “v” stand for?

Answer 25

u = object distance or height
v = image distance or height