Photo Electric Effect

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Test1 Max. Marks = 40

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1. The kinetic energy of an electron is 5 eV. Calculate the de-Broglie wavelength associated with it (h = 6.6 x 10⁻³⁴ Js, me = 9.1 x 10⁻³¹ kg)

4 points

(a) 5.47 Å

(b) 10.9 Å

(d) None of these

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2. If the kinetic energy of a free electron doubles, its de-Broglie wavelength changes by the factor

4 points

(a)

(b)

(c)

(d)

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3. de-Broglie wavelength of a body of mass m and kinetic energy E is given by

4 points

(a)

(b)

(c)

(d)

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4. An important spectral emission line has a wavelength of 21 cm. The corresponding photon energy is

(h = 6.6 x 10⁻³⁴ Js, c = 3 x 10⁻³¹ m s⁻¹)

4 points

(a) 5.9 x 10⁻⁴ eV

(b) 5.9 x 10⁻⁶ eV

(d) 11.8 x 10⁻⁶ eV

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5. Energy of photon whose frequency is 10¹² MHz will be

4 points

(a) 4.14 x 10³ keV

(b) 4.14 x 10² eV

(d) 4.14 x 10³ eV

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6. The work function of metal is 1 eV. Light of wavelength 3000 Å is incident on this metal surface. The velocity of emitted photo-electrons will be

4 points

(a) 10 m s⁻¹

(b) 1 x 10³ m s⁻¹

(d) 1 x 10⁶ m s⁻¹

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7. The photoelectric threshold wavelength for a metal surface is 6600 Å. The work function for this is

4 points

(a) 1.87 V

(b) 1.87 eV

(d) 0.18 eV

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8. A radio transmitter operates at a frequency of 880 kHz and a power of 10 kW. The number of photons emitted per second are

4 points

(a) 1.72 x 10³¹

(b) 1327 x 10³⁴

(d) 0.075 x 10³⁴

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9. A photoelectric cell is illuminated by a point source of light 1 m away. When the source is shifted to 2 m then

4 points

(a) Number of electrons emitted is half the initial number

(b) Each emitted electron carries half the initial energy

(d) Each emitted electron carries one quarter of the initial energy

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10. An X-ray tube is operated at 50 kV. The minimum wavelength produced is

4 points

(a) 0.5 Å

(b) 0.75 Å

(d) 1 Å

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