Chapter 5 - Lenses

Question 0

What is short sight and what lens is suitable ?

Answer 0

A short-sighted person can see nearby objects clearly but cannot bring distant objects into focus.Can be corrected using a Concave lens.

Question 1

Define:
Converging lens
Diverging lens

Answer 1

Parallel beam which passes through a convex lens converges.

Parallel beam which passes through a concave lens diverges.

Question 2

What is long sight and what lens is suitable ?

Answer 2

A long sighted person can see distant objects clearly but cannot bring nearby objects into focus. Can be corrected using a Convex lens.

Question 3

Explain:

Power of a lens

Answer 3

The power of the lens with the short focal length is larger. P=1/f

Question 4

Describe:

Controlling the light entering the eye

Answer 4

The iris controls the amount of light entering the eye by changing the size of the pupil, when bright the pupil is small and when dark big.

Question 5

Describe:

The focusing system of the eye

Answer 5

The cornea and the crystalline lens together form a converging system. The aqueous humour and the vitreous humour also form part of this focusing system.

Question 6

Describe:

The image formed on the retina

Answer 6

The retina is a light sensitive screen at the back of the eye. When light strikes the retina, electrical messages are sent to the brain through the optic nerve. The image on the retina is upside down and the brain views it right side up.

Question 7

Describe:

Power of accommodation

Answer 7

Is the ability to focus a real image of an object on the retina, whether the object is far from or near the eye.The ciliary muscles change the shape of the lens.

Question 8

If object is viewed at a large distance away:

If object is viewed at a short distance away:

Answer 8

The image is brought to focus on the retina with the ciliary muscles relaxed.
The image would be brought into focus behind the eye and would be seen blurry.