Atoms · Question 20

Electrons of mass m with de-Broglie wavelength fall on the target in an X-ray tube. The cutoff wavelength ( 0) of the emitted X-ray is

1. 0 = 2mc 2h
2. 0 = 2hmc
3. 0 = 2m2c2 3h2
4. 0 =

If an electron in a hydrogen atom jumps from the 3rd orbit to the 2nd orbit, it emits a photon of wavelength . When it jumps from the 4th orbit to the 3rd orbit, the corresponding wavelength of the photon will be

1. 1625
2. 916
3. 207
4. 2013

In the spectrum of hydrogen, the ratio of the longest wavelength in the Lyman series to the longest wavelength in the Balmer series is

1. 275
2. 527
3. 49
4. 94

Consider 3rd orbit of He+ (Helium), using non-relativistic approach, the speed of electron in this orbit will be [given K = 9 109 constant, Z = 2 and h (Planck's Constant) = 6.6 10-34 J s]

1. 0.73 106 m/s
2. 3.0 108 m/s
3. 2.92 106 m/s
4. 1.46 106 m/s

Hydrogen atom in ground state is excited by a monochromatic radiation of = 975 A. Number of spectral lines in the resulting spectrum emitted will be

1. 3
2. 2
3. 6
4. 10

Ratio of longest wave lengths corresponding to Lyman and Balmer series in hydrogen spectrum is

1. 729
2. 931
3. 527
4. 323

An electron in hydrogen atom makes a transition n1 n2 where n1 and n2 are principal quantum numbers of the two states. Assuming Bohr's model to be valid, the time period of the electron in the initial state is eight times that in the final state. The possible values of n1 and n2 are

1. n1 = 6 and n2 = 2
2. n1 = 8 and n2 = 1
3. n1 = 8 and n2 = 2
4. n1 = 4 and n2 = 2

The transition from the state n = 3 to n = 1 in a hydrogen like atom results in ultraviolet radiation. Infrared radiation will be obtained in the transition from

1. 2 1
2. 3 2
3. 4 2
4. 4 3

Electron in hydrogen atom first jumps from third excited state to second excited state and then from second excited to the first excited state. The ratio of the wavelengths 1 : 2 emitted in the two cases is

1. 75
2. 2720
3. 275
4. 207

An electron of a stationary hydrogen atom passes from the fifth energy level to the ground level. The velocity that the atom acquired as a result of photon emission will be

1. 24hR25m
2. 25hR24m
3. 25m24hR
4. 24m25hR