| Question (1):
The change in focal length of an eye lens to focus the image of objects at varying distances is done by the action of ________. |
| 1. |
pupil |
| 2. |
ciliary muscles
|
| 3. |
retina |
| 4. |
blind spot |
|
| Ans: 2 |
|
| Question (2):
Far point of a normal eye is situated at _________. |
| 1. |
25 cm |
| 2. |
infinity
|
| 3. |
50 cm |
| 4. |
400 cm |
|
| Ans: 2 |
|
| Question (3):
A long-sighted person cannot see objects nearer to his eye than 50 cm. To enable him to read a book 25 cm away, he should use spectacle lenses whose power in dioptres is ____. |
|
|
| Ans: 4 |
|
| Question (4):
The process by which a beam of white light splits into its constituent colours is known as _________. |
| 1. |
reflection |
| 2. |
dispersion
|
| 3. |
divergence |
| 4. |
convergence |
|
| Ans: 2 |
|
| Question (5):
The band of colours obtained due to dispersion is known as ______________. |
| 1. |
spectrum |
| 2. |
rainbow
|
| 3. |
image |
| 4. |
mirage |
|
| Ans: |
|
| Question (6):
Power of a lens is expressed in |
| 1. |
dioptre |
| 2. |
cm
|
| 3. |
metre |
| 4. |
millimetre |
|
| Ans: 1 |
|
| Question (7):
1 D is the power of a lens of focal length ______ cm. |
| 1. |
100 |
| 2. |
10
|
| 3. |
1/100 |
| 4. |
1/10 |
|
| Ans: 1 |
|
| Question (8):
Hypermetropia is rectified by using |
| 1. |
convex lens |
| 2. |
concave lens
|
| 3. |
cylindrical lens |
| 4. |
progressive lens |
|
| Ans: 1 |
|
| Question (9):
Reciprocal of focal length in metres is known as the ______ of a lens. |
| 1. |
focus |
| 2. |
power
|
| 3. |
power of accommodation |
| 4. |
far point |
|
| Ans: 2 |
|
| Question (10):
The power of a convex lens of focal length 50 cm is ______. |
| 1. |
+ 2 D |
| 2. |
- 2 D
|
| 3. |
50 D |
| 4. |
- 5 D |
|
| Ans: 1 |
|
| Question (11):
Two lenses having powers +2D and -4D respectively are put together. Power of the combination would be |
| 1. |
-2 D |
| 2. |
+2 D
|
| 3. |
-4 D |
| 4. |
+4 D |
|
| Ans: 1 |
|
| Question (12):
The fluid between the retina and the lens is called _______. |
| 1. |
aqueous humour |
| 2. |
vitreous humour
|
| 3. |
aqua |
| 4. |
humus |
|
| Ans: 2 |
|
| Question (13):
Two thin lenses of power +5D and -2D are put in contact with each other. Focal length of the combination is |
| 1. |
+3 m |
| 2. |
-3 m
|
| 3. |
0.33 m |
| 4. |
-0.33 m |
|
| Ans: 3 |
|
| Question (14):
The least distance of distinct vision for infants is _________. |
| 1. |
15 cm |
| 2. |
20 cm
|
| 3. |
25 cm |
| 4. |
5 cm |
|
| Ans: 4 |
|
| Question (15):
The focal length of a lens whose power is -1.5 D is _______. |
| 1. |
-66.66 cm |
| 2. |
+ 1.5 m
|
| 3. |
+ 66.66 cm |
| 4. |
-1.5 m |
|
| Ans: 1 |
|
