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- DAluminiu
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The working of optical instruments like camera, microscope, telescope, etc. having glass lenses is based on a phenomenon of light. Identify the phenomenon.
Which of the following statement is not correct
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(a) Photographic plates are sensitive to infrared rays |
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(b) Photographic plates are sensitive to ultraviolet rays |
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(c) Infra-red rays are invisible but can cast shadows like visible light |
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(d) Infrared photons have more energy than photons of visible light |
Consider a radioactive material of half-life 1.0 minute. If one of the nuclei decays now, the next one will decay
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(a) After 1 minute |
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(b) After |
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(c) After |
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(d) After any time |

The slopes of anode and mutual characteristics of a triode are 0.02 mA V–1 and 1 mA V–1 respectively. What is the amplification factor of the valve
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(a) 5 |
(b) 50 |
(c) 500 |
(d) 0.5 |
Two short magnets with their axes horizontal and perpendicular to the magnetic meridian are placed with their centres 40 cm east and 50 cm west of magnetic needle. If the needle remains undeflected, the ratio of their magnetic moments
is
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(a) 4 : 5 |
(b) 16 : 25 |
(c) 64 : 125 |
(d) 2 : |
Assertion : Fuse wire must have high resistance and low melting point.
Reason : Fuse is used for small current flow only.
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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. |