Optics

Question 1

Diffuse reflection

Answer 1

Light is scattered in all directions due to the rough surface

Question 2

Regular reflection

Answer 2

Light is reflected off as it’s shown due to a smooth surface eg. Plane mirror

Question 3

Laws of reflection

Answer 3

The incident Ray, the normal at the point of incidence & the reflected Ray all lie on the same plane

Angle of incidence =angle of reflection

Question 4

Virtual image

Answer 4

Formed by the apparent intersection of Rays

Question 5

Real image

Answer 5

Formed by the actual intersection of light rays

Question 6

Lateral inversion

Answer 6

the apparent reversal of the mirror image’s left and right when compared with the object.

Question 7

Mirror parallax

Answer 7

Apparent movement of one object relative to another due to the motion of the observer

Furthest object seems to move

Question 8

State of no parallax

Answer 8

In the same line
No distance between them
Can be used to locate an object in the mirror

Question 9

Concave mirror

Answer 9

Caves in

Question 10

Rules for drawing a ray diagram

Answer 10

Parallel & focal point
Focal point & parallel
Centre of curvature

Question 11

Uses of concave mirrors

Answer 11

Searchlights, floodlights, headlights in a car, shaving mirrors

Question 12

Convex mirror

Answer 12

Image is always diminished upright & virtual

Question 13

Uses of convex mirrors

Answer 13

Door mirror of a car
In shops to deter shoplifters
At concealed entrance to give a view of oncoming traffic

Question 14

Mirror formula

Answer 14

Real image 1/u + 1/v =1/f
Virtual image 1/u - 1/v =1/f
Magnification v/u

Question 15

Reflection

Answer 15

The bouncing of light off an object

Question 16

Precautions that should be taken when measuring the distance in the focal lenght of a concave mirror experiment

Answer 16

Measure from the back of the mirror/ measure from the centre of the mirror/ avoid parallax error/ensure image is sharp

Question 17

How to find an approximate value for the focal lentgh

Answer 17

focus the image of a distinct object on the screen

Measure the distance between the mirror and the screen.

Question 18

Refraction

Answer 18

the bending of a ray of light when it goes from one medium to another

Question 19

Laws of Refraction

Answer 19

the incident ray, the normal at the point of incidence and the refracted ray all lie on the same plane

Snell’s Law: the ratio of the sin of the angle of incidence to the sin of the angle of refraction is a constant called the Refractive Index

Question 20

Refractive Index

Answer 20

Sini/Sinr = n where n is a constant

Question 21

Refractive Index of a medium

Answer 21

real depth/ apparent depth

Question 22

Critical Angle (C)

Answer 22

when light travels from a denser to a rarer medium, the angle of incidence, whose corresponding angle of refraction is 90 degrees is called the critical angle

Question 23

Critical Angle Formula

Answer 23

n = SinC/Sin90 = SinC/1 = SinC

Question 24

Refractive index in terms of relative speeds

Answer 24

N = C1/C2 = Speed of air/ R.I of medium

Question 25

Total Internal Reflection

Answer 25

If the angle of incidence in the denser of the two media is greater than the critical angle, the light is reflected back into the denser medium

Question 26

Application of Total Internal Reflection

Answer 26

Reflective road signs, Optical Fibres, Endoscopes, Periscopes

Question 27

Optical Fibre

Answer 27

Very thin transparent rod (usually glass) through which light can travel by total internal reflection

Question 28

How Optical Fibres work

Answer 28

Light enters one end of the fibre & strikes the boundary between the two materials, at an angle greater than the critical angle, resulting in total internal reflection

Question 29

How can light escape an optical fibre?

Answer 29

If it’s bent too much

If it comes into contact with another fibre

Question 30

Uses of an Optical Fibre

Answer 30

Telecommunications and Endoscopes

Question 31

Advantages of Optical Fibres over copper conductors

Answer 31

Less interference/ boosted less often/ cheaper raw material/ occupies less space/ doesn’t corrode

Question 32

Experiment: to verify Snell’s Law and Hence measure the R.I of Glass - Sources of Error/ Precautions

Answer 32

Using small angles of incidence result in large percentage errors

Place two dots far apart on the incident and refracted light beam to accurately locate the beams

Question 33

Convex Lens

Answer 33

If the image is outside the focus the image is real and inverted
If it’s inside the focus the image is virtual and upright

Question 34

How light refracts in a convex lens

Answer 34

A ray strikes the optic centre, passes straight through the lens
A ray that travels parallel to the axis strikes the focus point on the other side of the lens
A ray which passes through the focus point and then strikes the lens, emerges parallel to the axis

Question 35

Concave lens diagrams

Answer 35

From top of the object to the lens parallel to the principal axis and up as if coming from focal point.

From top of object to the lens as if passing through the centre of curvature

Question 36

The power of then lens

Answer 36

1/ focal length

Unit is (m) -1

Question 37

Equation: if two lenses are placed in contact the focal length f of the combination is

Answer 37

1/f= 1/f(1) + 1/f(2)

Question 38

Power of Accommodation

Answer 38

The eyes ability to focus a real image of an object on the retina, whether the object is near of far away from the eye

Question 39

Short sighted person

Answer 39

Can see nearby objects but cannot bring distance objects into focus

Question 40

Long sighted person

Answer 40

Can see distant objects but cannot bring nearby objects into focus. It is corrected with a concave lens