The coefficient of performance of a refrigerator is \(5.\) If the temperature inside the freezer is \(-20^\circ \text{C},\) the temperature of the surroundings to which it rejects heat is:
1. \(31^\circ \text{C}\)
2. \(41^\circ \text{C}\)
3. \(11^\circ \text{C}\)
4. \(21^\circ \text{C}\)
1. \(31^\circ \text{C}\)
2. \(41^\circ \text{C}\)
3. \(11^\circ \text{C}\)
4. \(21^\circ \text{C}\)
A photoelectric surface is illuminated successively by the monochromatic light of wavelength \(\lambda\) and \(\frac{\lambda}{2}\). If the maximum kinetic energy of the emitted photoelectrons in the second case is \(3\) times that in the first case, the work function of the surface of the mineral is:
[\(h\) = Plank’s constant, \(c\) = speed of light]
| 1. | \(\dfrac{hc}{2\lambda}\) | 2. | \(\dfrac{hc}{\lambda}\) |
| 3. | \(\dfrac{2hc}{\lambda}\) | 4. | \(\dfrac{hc}{3\lambda}\) |
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. | \(\frac{L}{l}\) |
Two slits in Young’s experiment have widths in the ratio of \(1:25.\) The ratio of intensity at the maxima and minima in the interference pattern \(\dfrac{I_{max}}{I_{min}}\) is:
| 1. | \(\dfrac{9}{4}\) | 2. | \(\dfrac{121}{49}\) |
| 3. | \(\dfrac{49}{121}\) | 4. | \(\dfrac{4}{9}\) |
Water rises to height '\(h\)' in a capillary tube. If the length of capillary tube above the surface of the water is made less than \('h'\), then:
| 1. | water does not rise at all. |
| 2. | water rises up to the tip of capillary tube and then starts overflowing like a fountain. |
| 3. | water rises up to the top of capillary tube and stays there without overflowing. |
| 4. | water rises up to a point a little below the top and stays there. |
| 1. | \(\dfrac{2}{3}\) | 2. | \(\dfrac{3}{4}\) |
| 3. | \(2\) | 4. | \(\dfrac{1}{2}\) |
A circuit contains an ammeter, a battery of \(30~\text{V},\) and a resistance \(40.8~\Omega\) all connected in series. If the ammeter has a coil of resistance \(480~\Omega\) and a shunt of \(20~\Omega,\) then the reading in the ammeter will be:
1. \(0.5~\text{A}\)
2. \(0.02~\text{A}\)
3. \(2~\text{A}\)
4. \(1~\text{A}\)
The value of the coefficient of volume expansion of glycerine is \(5\times10^{-4}~\text{K}^{-1}.\) The fractional change in the density of glycerine for a rise of \(40^\circ \text{C}\) in its temperature is:
| 1. | \(0.015\) | 2. | \(0.020\) |
| 3. | \(0.025\) | 4. | \(0.010\) |
The heart of a man pumps \(5~\text{L}\) of blood through the arteries per minute at a pressure of \(150~\text{mm}\) of mercury. If the density of mercury is \(13.6\times10^{3}~\text{kg/m}^{3}\) \(g = 10~\text{m/s}^2,\) then the power of the heart in watts is:
| 1. | \(1.70\) | 2. | \(2.35\) |
| 3. | \(3.0\) | 4. | \(1.50\) |
The prism will:
| 1. | separate the blue colour part from the red and green colour. |
| 2. | separate all three colours from one another. |
| 3. | not separate the three colours at all. |
| 4. | separate the red colour part from the green and blue colours. |
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