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
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NEET MCQ Books for XIth & XIIth Physics, Chemistry & BiologyWhen 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
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NEET MCQ Books for XIth & XIIth Physics, Chemistry & BiologyThe 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
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NEET MCQ Books for XIth & XIIth Physics, Chemistry & Biology