A plane mirror is placed at the bottom of a fish tank filled with water of refractive index . The fish is at a height 10 cm above the plane mirror. An observer O is vertically above the fish outside water. The apparent distance between the fish and its image is:
1. 15 cm
2. 30 cm
3. 35 cm
4. 45 cm
A liquid of refractive index is placed between two identical planoconvex-lenses touching each other at their spherical surfaces of radius R. If the refractive index of the lens is 1.50, then the lens behaves as:
1. | a convergent with power \(\mathrm{P}=\frac{1}{3 R}\) |
2. | a convergent with power \(\mathrm{P}=\frac{1}{6 R}\) |
3. | a divergent with power \(\mathrm{P}=\frac{1}{3 R}\) |
4. | a divergent with power \(\mathrm{P}=\frac{1}{6 R}\) |
If there is no emergent light through a prism of refracting angle \(60^{\circ},\) whatever may be the angle of incidence, then the minimum value of the refractive index of the material of the prism is:
1. 2
2.
3. 1.5
4.
The Refractive index of material of an equilateral prism is . Angle of incidence for minimum deviation is:
1. \(60^{\circ}\)
2. \(45^{\circ}\)
3. \(30^{\circ}\)
4. \(15^{\circ}\)
The minimum magnifying power of an astronomical telescope is 40. If the length of the telescope is 205 cm, then the focal length of its field lens is:
1. 5 cm
2. 200 cm
3. 40 cm
4. 140 cm
A boy with defective eye-sight cannot see things beyond 50 cm. The corrective lens required has the power:
1. +1 D
2. +2 D
3. -1 D
4. -2 D
If \(C_1,~C_2 ~\mathrm{and}~C_3\) are the critical angle of glass-air interface for red, violet and yellow color, then:
1. | \(C_3>C_2>C_1\) | 2. | \(C_1>C_2>C_3\) |
3. | \(C_1=C_2=C_3\) | 4. | \(C_1>C_3>C_2\) |
An astronomical telescope has angular magnification of 40 in its normal adjustment. If focal length of eyepiece is 5 cm, the length of the telescope is:
1. 190 cm
2. 200 cm
3. 205 cm
4. 210 cm
The focal length of a convex lens is 40 cm and the size of the inverted image formed is half of the object. The distance of the object is:
1. | 60 cm | 2. | 120 cm |
3. | 30 cm | 4. | 180 cm |
The condition of minimum deviation is achieved in an equilateral prism kept on the prism table of a spectrometer. If the angle of incidence is \(50^{\circ}\), the angle of deviation is:
1. \(25^{\circ}\)
2. \(40^{\circ}\)
3. \(50^{\circ}\)
4. \(60^{\circ}\)