# A 100-watt bulb emits monochromatic light of wavelength 400 nm. The number of photons emitted per second by the bulb is- 1. 4 2.  3.  4. 2

Subtopic:  Photo Electric Effect |
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When electromagnetic radiation of wavelength 300 nm falls on the surface of sodium, electrons are emitted with a kinetic energy of 1.68 ×105 J mol–1. The minimum energy needed to remove an electron from sodium and the maximum wavelength that will cause a photoelectron to be emitted are respectively-

1. 2.31 × 105 J mol–1, 517 nm

2. 23.1 × 105 J mol–1, 517 nm

3. 3.31 × 105 J mol–1, 417 nm

4. 33.1 × 105 J mol–1, 417 nm

Subtopic:  Photo Electric Effect |
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The threshold frequency νo for a metal is 7.0 ×1014 s–1. The kinetic energy of an electron emitted when radiation of frequency ν =1.0 ×1015 s–1 hits the metal, is-

1. 19.88 ×10–19 J

2. 1.988 ×10–19 J

3. 1.988 ×10–20 J

4. 19.88 ×10–17 J

Subtopic:  Photo Electric Effect |
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The frequency and wavelength of a photon emitted during a transition from n = 5 state to the n = 2 state in the hydrogen atom  are respectively-

1.  $$6.91\times10 ^{14} Hz$$;   543 nm

2. $$7.91\times10 ^{14} Hz$$; 434 nm

3. $$6.91\times10 ^{14} Hz$$; 434

4. $$7.91\times10 ^{14} Hz$$; 343 nm

Subtopic:  Hydrogen Spectra |
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The energy and the radius of the first orbit of He+ are respectively-

1. $$-8.72\times 10^{-18}J$$; 0.02645 nm

2. $$8.72\times 10^{-18}J$$; 0.02645 nm

3. $$-7.82\times 10^{-18}J$$ ; 0.03655 nm

4. $$7.82\times 10^{-18}J$$; 0.03655 nm

Subtopic:  Hydrogen Spectra |
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The wavelength of a ball of mass 0.1 kg moving with a velocity of 10 m s–1 is-

1. 662.6 × 10–34 m

2. 66.26 × 10–34 m

3. 6.626 × 10–34 m

4. 6.626 × 10–36 m

Subtopic:  De Broglie Equation |
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Kinetic Energy of an electron is 3.0×10–25 J. The wavelength of the electron will be-

1. 886.7 nm

2. 896.7 nm

3. 990.7 nm

4. 880.7 nm

Subtopic:  De Broglie Equation |
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The mass of a photon with wavelength 3.6 Å is-

1. 5.135 × 10–29 kg

2. 61.35 × 10–33 kg

3. 613.5 × 10–29 kg

4. 6.135 × 10–33 kg

Subtopic:  De Broglie Equation |
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A microscope using suitable photons is employed to locate an electron in an atom within a distance of 0.1 Å. The uncertainty involved in the measurement of its velocity is-

1. 5.79×106 m s–1

2. 57.9×106 m s–1

3. 5.79×107 m s–1

4. 57.9×107 m s–1

Subtopic:  Heisenberg Uncertainty Principle |
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A golf ball has a mass of 40g, and a speed of 45 m/s. If the speed can be measured within the accuracy of 2%, the uncertainty in the position is-

1. 1.46×10–23 m

2. 14.6×10–33 m

3. 1.46×10–23 m

4. 1.46×10–33 m

Subtopic:  Heisenberg Uncertainty Principle |
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