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Which one of the following is true in photoelectric emission
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(a) Photoelectric current is directly proportional to the amplitude of light of a given frequency |
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(b) Photoelectric current is directly proportional to the intensity of light of a given frequency at moderate intensities |
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(c) Above the threshold frequency, the maximum K.E. of photoelectrons is inversely proportional to the frequency of incident light |
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(d) The threshold frequency depends upon the wavelength of incident light |
In Bohr model of the hydrogen atom, the lowest orbit corresponds to
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(a) Infinite energy |
(b) The maximum energy |
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(c) The minimum energy |
(d) Zero energy |
An example of a diamagnetic substance is
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(a) Aluminium |
(b) Copper |
(c) Iron |
(d) Nickel |
A bar magnet of length 3 cm has points A and B along its axis at distances of 24 cm and 48 cm on the opposite sides. Ratio of magnetic fields at these points will be
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(a) 8 |
(b) 1/2 |
(c) 3 |
(d) 4 |
The potential gradient along the length of a uniform wire is 10 volt/metre. B and C are the two points at 30 cm and 60 cm point on a meter scale fitted along the wire. The potential difference between B and C will be
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(a) 3 volt |
(b) 0.4 volt |
(c) 7 volt |
(d) 4 volt |
If the radioactive decay constant of radium is 1.07 
per year, then its half life period is approximately equal to
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(a) 8,900 years |
(b) 7,000 years |
(c) 6,476 years |
(d) 2,520 years |
The rays parallel and close to the principal axis are called:
Radio wave diffract around building although light waves do not. The reason is that radio waves
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(a) Travel with speed larger than c |
(b) Have much larger wavelength than light |
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(c) Carry news |
(d) Are not electromagnetic waves |
