Ultraviolet radiations of 6.2eV falls on an aluminium surface (work function 4.2 eV). The kinetic energy in joules of the fastest electron emitted is approximately
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(a) 3.2 |
(b) 3.2 |
(c) 3.2 |
(d) 3.2 |
(b) 3.2 
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Assertion : The induced emf in a conducting loop of wire will be non zero when it rotates in a uniform magnetic field.
Reason : The emf is induced due to change in magnetic flux.
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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. |
Positive rays was discovered by
|
(a) Thomson |
(b) Goldstem |
(c) W. Crookes |
(d) Rutherford |
Two thin lenses of focal lengths 20 cm and 25 cm are placed in contact convex. The effective power of the combination is
|
(a) 45 dioptres |
(b) 9 dioptres |
(c) 1/9 dioptre |
(d) 6 dioptres |
