1. | Difference between apparent and real depth of the pond |
2. | Mirage on hot summer days |
3. | Brilliance of the diamond |
4. | Working of optical fibre |
A ray of light travelling in a transparent medium of refractive index \(\mu\) falls on a surface separating the medium from the air at an angle of incidence of \(45^{\circ}\). For which of the following value of \(\mu\), the ray can undergo total internal reflection?
1. \(\mu = 1.33\)
2. \(\mu =1.40\)
3. \(\mu=1.50\)
4. \(\mu = 1.25\)
A lens having focal length \(f\) and aperture of diameter \(d\) forms an image of intensity \(I\). An aperture of diameter \(\frac{d}{2}\) in central region of lens is covered by a black paper. The focal length of lens and intensity of the image now will be respectively:
1. \(f\) and \(\frac{I}{4}\)
2. \(\frac{3f}{4}\) and \(\frac{I}{2}\)
3. \(f\) and \(\frac{3I}{4}\)
4. \(\frac{f}{2}\) and \(\frac{I}{2}\)
Two thin lenses of focal lengths f1 and f2 are in contact and coaxial. The power of the combination is:
1.
2.
3.
4. None of the above
A boy is trying to start a fire by focusing sunlight on a piece of paper using an equiconvex lens of a focal length of \(10\) cm. The diameter of the sun is \(1.39\times10^9\) m and its mean distance from the earth is \(1.5\times10^{11}\) m. What is the diameter of the sun's image on the paper?
1. | \(9.2\times10^{-4}\) m | 2. | \(6.5\times10^{-4}\) m |
3. | \(6.5\times10^{-5}\) m | 4. | \(12.4\times10^{-4}\) m |
1. | \(1.8 \times 10^8 ~\text{m/s}\) | 2. | \(2.4 \times 10^8~\text{m/s}\) |
3. | \(3.0 \times 10^8~\text{m/s}\) | 4. | \(1.2 \times 10^8~\text{m/s}\) |
The frequency of a light wave in a material is 2×1014 Hz and the wavelength is 5000 Å. The refractive index of the material will be:
1. 1.40
2. 1.50
3. 3.00
4. 1.33
A microscope is focused on a mark on a piece of paper and then a slab of glass of thickness 3 cm and a refractive index 1.5 is placed over the mark. How should the microscope be moved to get the mark in focus again?
1. 1 cm upward
2. 4.5 cm downward
3. 1 cm downward
4. 2 cm upward
A convex lens and a concave lens, each having the same focal length of 25 cm, are put in contact to form a combination of lenses. The power in dioptres of the combination is:
1. 25
2. 50
3. infinite
4. zero
1. | virtual, upright, height \(=0.5\) cm |
2. | real, inverted, height \(=4\) cm |
3. | real, inverted, height \(=1\) cm |
4. | virtual, upright, height \(=1\) cm |