A concave lens of focal length 25 cm produces an image the size of the object. The distance of the object from the lens is:
1. 225 cm
2. 250 cm
3. 150 cm
4. 175 cm
A convex mirror of focal length \(f\) forms an image which is \(\frac{1}{n}\) times the length of the object. The distance of the object from the mirror is:
1. \((n-1)f\)
2. \(\left( \frac{n-1}{n} \right)f\)
3. \(\left( \frac{n+1}{n} \right)f\)
4. \((n+1)f\)
A mark on the surface of sphere (µ = 3/2) is viewed from a diametrically opposite position. It appears to be at a distance \(15~\mathrm{cm}\) from its actual position. The radius of sphere is:
1. 15 cm
2. 5 cm
3. 7.5 cm
4. 2.5 cm
A light ray from the air is incident (as shown in the figure) at one end of glass fibre (refractive index µ = 1.5) making an incidence angle of 60° on the lateral surface so that it undergoes a total internal reflection. How much time would it take to traverse the straight fibre of a length of 1 km?
1. 3.33
2. 6.67
3. 5.77
4. 3.85
Choose the correct mirror image of the figure:
1. | 2. | ||
3. | 4. |
If there had been one eye of a man, then:
1. | image of the object would have been inverted |
2. | visible region would have decreased |
3. | image would have not been seen in three dimensional |
4. | Both (2) and (3) |
The near point of a person is 50 cm and the far point is 1.5 m. The spectacles required for reading purposes and for seeing distant objects are respectively:
1. + 2D, \(-\frac{2}{3}~D\)
2. \(+\frac{2}{3}~D\), - 2 D
3. - 2 D, \(+\frac{2}{3}~D\)
4. \(-\frac{2}{3}~D\), + 2 D
Focal lengths of objective and eyepiece of a compound microscope are 2 cm and 6.25 cm respectively. An object AB is placed at a distance of 2.5 cm from the objective which forms the image A'B' as shown in the figure. Maximum magnifying power in this case, will be:
1. | 10 | 2. | 20 |
3. | 5 | 4. | 25 |
If the space between two convex lenses of glass in the combination shown in the figure below is filled with water, then:
1. | the focal length of the system will decrease. |
2. | the focal length of the system will increase. |
3. | the power of the system will increase. |
4. | the power of the system will become infinite. |
An astronomical telescope has angular magnification of 20 in its normal adjustment. Focal length of eyepiece is 4 cm. Distance between objective and eyepiece is:
1. 80 cm
2. 84 cm
3. 76 cm
4. 90 cm