Mirrors

Question 1

Reflection is defined as

Answer 1

Light bouncing off an object

Question 2

What are the Laws of Reflection

Answer 2

1. The incident ray, normal at point of incident and the reflected ray all lie on the same plane
2. The angle of incidence is equal to the angle of reflection

Question 3

What is a virtual image

Answer 3

An image formed by a plane mirror

Question 4

The two types of spherical mirrors are

Answer 4

Concave and convex

Question 5

A real image is formed by……….

A virtual image is formed by………

Answer 5

The actual intersection of light rays (can be projected on screen)

The apparent intersection of light rays (cannot be projected on screen)

Question 6

Formulas

Answer 6

1. 1/f = 1/u + 1/v

2. Magnification= v/u

Question 7

In convex mirrors the image is always

Answer 7

Diminished, upright and virtual

Question 8

Uses of convex mirrors

Answer 8

1. Door mirror of a car
2. In shops to deter shoplifters
3. At concealed entrances to give view of ongoing traffic

Question 9

Experiment to measure the focal length of a concave mirror

Answer 9

Apparatus: Concave mirror, screen, lamp box, crossfire, metre stick, retort stand

Procedure:
First: focus image of a distant object onto screen. Then measure the distance between the mirror and the screen as your focal length.

1. Place ray box outside approximate focal length
2. Move screen until a clear inverted image of crossfire is obtained
3. Measure distance u from crossfire to mirror
4. Measure distance v from screen to mirror
5. Repeat procedure for different values of u
6. Calculate focal length of mirror using formula 1/f =1 /u + 1/v

Sources of Error

1. Determining when image is in sharpest focus repeat each time to get an average
2. Parallax error associated with measuring u and v ensure your line of sight is at right angles to metre stick
3. Take all measurements from back of mirror