Q. No.In an astronomical telescope in normal adjustment, a straight line of length \(L\) is drawn on the inside part of the objective lens. The eye-piece forms a real image of this line. The length of this image is \(l.\) The magnification of the telescope is:
1. \(\frac{L}{l}+1\)
2. \(\frac{L}{l}-1\)
3. \(\frac{L+1}{l-1}\)
4. \(\frac{L}{l}\)
A beam of light consisting of red, green, and blue colours is incident on a right-angled prism. The refractive index of the material of the prism for the red, green, and blue wavelengths is 1.39, 1.44, and 1.47 respectively.
The prism will:
| 1. | separate the blue colour part from the red and green colour |
| 2. | separate all the three colours from one another |
| 3. | not separate the three colours at all |
| 4. | separate the red color part from the green and blue colours |
Two identical thin plano-convex glass lenses (refractive index = 1.5) each having radius of curvature of 20 cm are placed with their convex surfaces in contact at the centre. The intervening space is filled with oil of a refractive index of 1.7. The focal length of the combination is:
1. -20 cm
2. -25 cm
3. -50 cm
4. 50 cm
2. \(180^\circ-2A\)
3. \(90^\circ-A\)
4. \(180^\circ+2A\)
If the focal length of the objective lens is increased then magnifying power of:
| 1. | microscope will increase but that of the telescope decrease. |
| 2. | microscope and telescope both will increase. |
| 3. | microscope and telescope both will decrease. |
| 4. | microscope will decrease but that of the telescope will increase. |
The angle of a prism is \(\text{A}.\) One of its refracting surfaces is silvered. Light rays falling at an angle of incidence \(2\text{A}\) on the first surface return back through the same path after suffering reflection at the silvered surface. The refractive index \(\mu,\) of the prism, is:
1. 2sinA
2. 2cosA
3. cosA
4. tanA
1. \(\frac{R}{2(\mu_1-\mu_2)}\)
2. \(\frac{R}{(\mu_1-\mu_2)}\)
3. \(\frac{2R}{(\mu_2-\mu_1)}\)
4. \(\frac{R}{2(\mu_1+\mu_2)}\)
For a normal eye, the cornea of the eye provides a converging power of 40 D and the least converging power of the eye lens behind the cornea is 20 D. Using this information, the distance between the retina and the cornea-eye lens can be estimated to be:
1. 2.5 cm
2. 1.67 cm
3. 1.5 cm
4. 5 cm
| 1. | the scattering of light. |
| 2. | the polarisation of light. |
| 3. | the colour of the sun. |
| 4. | the colour of the sky. |
1. \(45^\circ\)
2. \(30^\circ\)
3. \(55^\circ\)
4. \(50^\circ\)
© 2024 GoodEd Technologies Pvt. Ltd.