Chapter 2 – Structure of Atom
Assignment 3
Q.1. A 100 watt bulb emits electro-magnetic light of wavelength 400 nm. Calculate the number of photons emitted per second by the bulb.
[Ans: 2.01 × 1020 ]
Q.2. How many photons of light having a wavelength 400 nm are necessary to provide 1 J of energy ?
[Ans: 2.01 × 1018 photons ]
Q.3. Calculate the wave number for the longest wavelength transition in the Balmer series of atomic hydrogen.
[ Ans: 1.523 × 106 m–1 ]
Q.4. What is the wavelength of light emitted when the electron in hydrogen atom undergoes transition from an energy level with n = 4 to an energy level with n = 2 ? What is the colour of the radiation ?
[ Ans: 486 nm, bluish green colour ]
Q.5. The first line in Balmer series corresponds to n1 = 2 and n2 = 3 and the limiting line corresponds to n1 = 2 and n2 = ∞. Calculate the wavelengths of the first and limiting lines in Balmer series.
[ Ans: First line = 656 nm, limiting line = 364.7 nm. ]
Q.6. In the Rydberg equation, a spectral line corresponds to n1 = 3 and n2 = 5.
(i) Calculate the wavelength and frequency of this spectral line.
(ii) Which spectral series does this line belong to?
(iii) In which region of the electromagnetic spectrum, will this line fall ?
[ Ans: (i) 1282 nm, 2.34 × 1014 s–1 (ii) Paschen series (iii) infra-red region ]
Q.7. The wavelength of first spectral line in the Balmer series is 6561 Å. Calculate the wavelength of the second spectral line in Balmer series.
[ Ans: 4860 Å ]
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