HUMAN EYE AND COLOURFUL WORLD

Q1:- Name the optical phenomenon responsible for formation of RAINBOW?
Ans:- Refraction, internal reflection and dispersion of light.
Q2:- What is meant by scattering of light?
Ans:-Scattering is the bouncing off of electro-magnetic radiations by atoms and molecules of the medium through which they are propagating.
Q3:- Why different colours deviate through different angles on passing through a prism?
Ans:- This is because different colours have different wavelengths and glass has different refractive index for different wavelengths .
Q4:-Which phenomenon of vision is used in cinematography?
Ans:-Persistence of vision.
Q5:- The near point of the hypermetropic eye is 1metre.What is the power of the lens required to correct this defect. Assume that near point of the normal eye is 25cm.
Ans: – Since, the near point of the hypermetropic eye is1m (100cm), the lens used should be such that the rays of light starting from normal near point(25cm) appear to come from the near point of hypermetropic eye.
Thus,
u = -25cm
v =-100cm
1/f =1/v -1/u
f = uv/u-v
= (-25) x (-100)/ (-25) – (-100)
=100/3
=33.3cm
P = 100/f
= 100/33.3
= 3 D
Since the power is positive , lens must be convex.
Q6:-The far point of a myopic person is 80cm in front of the eye. What is the nature and power of the lens required to correct the problem?
Ans:- Distance of far point ,x =80cm
P =?
For viewing distant objects, focal length of the corrective lens
f = – x = -80cm
P = 100/f
= 100/-80
=-1.25 D
The Lens is concave.
Q7:- Danger Signals are red in colour, why?
Ans:-Due to its longer wavelength, red colour is least scattered by fog or smoke.Thus, the red is visible in the same colour from large distances.

Q.8.Why do we have two eyes for vision and not just one?

Ans. (a) It gives a wider field of view.
(b).The ability to detect faint objects is enhanced with two eyes instead of one.
(c). Our eyes are separated by a few centimeters; each eye sees a slightly different image. Our brain combines the two images into one and thus provides a three-dimensional perception of the objects.

Q.9.What is persistence of vision?

Ans.The ability of an eye to continue to see the image of an object for a very short duration even after the removal of the object is called persistence of the vision. In human eye, vision persists for 1/16th of a second after removal of the object.
http://ping.fm/q2BE8