Question 1
Question: 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 |
Answer: 2
Question 2
Question: Far point of a normal eye is situated at _________.
| 1. | 25 cm |
| 2. | infinity |
| 3. | 50 cm |
| 4. | 400 cm |
Answer: 2
Question 3
Question: 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 ____.
| 1. | -6 |
| 2. | -4 |
| 3. | -2 |
| 4. | + 4 |
Answer: 4
Question 4
Question: 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 |
Answer: 2
Question 5
Question: The band of colours obtained due to dispersion is known as ______________.
| 1. | spectrum |
| 2. | rainbow |
| 3. | image |
| 4. | mirage |
Answer:
Question 6
Question: Power of a lens is expressed in
| 1. | dioptre |
| 2. | cm |
| 3. | metre |
| 4. | millimetre |
Answer: 1
Question 7
Question: 1 D is the power of a lens of focal length ______ cm.
| 1. | 100 |
| 2. | 10 |
| 3. | 1/100 |
| 4. | 1/10 |
Answer: 1
Question 8
Question: Hypermetropia is rectified by using
| 1. | convex lens |
| 2. | concave lens |
| 3. | cylindrical lens |
| 4. | progressive lens |
Answer: 1
Question 9
Question: Reciprocal of focal length in metres is known as the ______ of a lens.
| 1. | focus |
| 2. | power |
| 3. | power of accommodation |
| 4. | far point |
Answer: 2
Question 10
Question: The power of a convex lens of focal length 50 cm is ______.
| 1. | + 2 D |
| 2. | - 2 D |
| 3. | 50 D |
| 4. | - 5 D |
Answer: 1
Question 11
Question: 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 |
Answer: 1
Question 12
Question: The fluid between the retina and the lens is called _______.
| 1. | aqueous humour |
| 2. | vitreous humour |
| 3. | aqua |
| 4. | humus |
Answer: 2
Question 13
Question: 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 |
Answer: 3
Question 14
Question: The least distance of distinct vision for infants is _________.
| 1. | 15 cm |
| 2. | 20 cm |
| 3. | 25 cm |
| 4. | 5 cm |
Answer: 4
Question 15
Question: 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 |
Answer: 1
