Explanation:
The Rayleigh criterion is the generally accepted criterion for the minimum resolvable detail - the imaging process is said to be diffraction-limited when the first diffraction minimum of the image of one source point coincides with the maximum of another.
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A coil of self inductance 50 henry is joined to the terminals of a battery of e.m.f. 2 volts through a resistance of 10 ohm and a steady current is flowing through the circuit. If the battery is now disconnected, the time in which the current will decay to 1/e of its steady value is
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(a) 500 seconds |
(b) 50 seconds |
(c) 5 seconds |
(d) 0.5 seconds |
$\frac{1}{4}\text{mgR}$
$\frac{1}{2}\text{mgR}$
$\text{mgR}$
$2\text{mgR}$
Assertion : The colour of the green flower seen through red glass appears to be dark.
Reason : Red glass transmits only red light.
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(a) If both assertion and reason are true and the reason is the correct explanation of the assertion. |
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(b) If both assertion and reason are true but reason is not the correct explanation of the assertion. |
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(c) If assertion is true but reason is false. |
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(d) If the assertion and reason both are false. |
The focal length of a lens of refractive index $\mu$ is f. If the lens is immersed in a liquid of refractive index $\mu$ then the focal length of lens is:
For a thermocouple the neutral temperature is 270℃ when its cold junction is at 20℃. What will be the neutral temperature and the temperature of inversion when the temperature of cold junction is increased to 40 ℃
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(a) 290℃, 580℃ |
(b) 270℃, 580℃ |
(c) 270℃, 500 ℃ |
(d) 290 ℃, 540 ℃ |
The essential distinction between X-rays and γ - rays is that
| (a) γ- rays have smaller wavelength than X-rays |
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(b) γ - rays emanate from nucleus while X-rays emanate from outer part of the atom |
| (c) γ- rays have greater ionizing power than X-rays |
| (d) γ- rays are more penetrating than X-rays |
An electric motor operating on a 60 V dc supply draws a current of 10 A. If the efficiency of the motor is 50%, the resistance of its winding is
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(a) 3Ω |
(b) 6 Ω |
(c) 15 Ω |
(d) 30 Ω |