12th class (Fsc) Physics unit 9 MCQs
chapter 9 MCQs 12th Class physics
Atomic Spectra:
1. We can find from de-Broglie formula:
a. Speed of wave
b. Wavelength
c. Frequency
d. Amplitude
2. The following gas was identified in the sun using spectroscopy:
a. Carbon
b. Hydrogen
c. Nitrogen
d. Helium
3. Production of X-rays is the reverse process of:
a. Pair annihilation
b. Compton effect
c. Photo electric effect
d. Pair production
4. Ballmer series lies in region of electromagnetic spectrum:
a. Ultraviolet
b. Infrared
c. Fra infrared
d. Visible
5. The shortest wave length in bracket series has wave length:
a. 16RH
b. 16/RH
c. 4RH
d. RH/16
6. The energy of electron of the 4th orbit in hydrogen atom is:
a. -13.60 eV
b. -2.51 eV
c. -0.85 eV
d. -3.50 eV
7. Radius of first Bohr’s orbit is:
a. 0.053µm
b. 0.053nm
c. 0.053m
d. 0.053mm
8. Which series lies in the ultraviolet region:
a. Ptund series
b. Ballmer series
c. Lyman series
d. Bracket series
9. Rydberg constant has value:
a. 3×108m-1
b. 1.0974×107m-1
c. 1.6×1019m-1
d. 6.02×10-34m-1
10. Second postulate of Bohr’s atomic model is:
a. mv = nhr/2π
b. mvr = nh/2π
c. mv = 2π/nh
d. mvr = 2πnh
11. In an electronic transition atom cannot emit:
a. Ultraviolet radiations
b. Infrared radiations
c. Y-radiations
d. Visible radiations
12. For Paschen series, the value of “n” starts from:
a. 6
b. 2
c. 8
d. 4
13. Balmer empirical formula explains the electromagnetic radiation of any excited atom in terms of their:
a. Wavelength
b. Energy
c. Momentum
d. Mass
14. Photons emitted in inner shell transition are:
a. Characteristic X rays
b. Continuous X-rays
c. Energetic X-rays
d. Discontinuous X rays
15. Production of X-rays is reverse process of:
a. Annihilation
b. Photo-electric effect
c. Pair production
d. Compton effect
16. The line radiations emitted from hydrogen filled discharge tube can be analyzed into:
a. Continuous spectrum
b. Band spectrum
c. Absorption spectrum
d. Line spectrum
17. Normally electron can reside in excited state for about:
a. 10-6s
b. 10-3s
c. 108s
d. 10-8s
18. First spectral series of hydrogen atom was discovered by:
a. Balmer
b. Lyman
c. Paschen
d. Rydberg
19. Which is not true for X-rays?
a. X-rays consist of electromagnetic waves
b. X-rays are not defeated by electric field
c. X-rays can be diffracted by grating
d. X-rays are polarized
20. The rest mass of X-ray photon is:
a. 1.67×10-27kg
b. Infinite
c. Zero
d. 9.1×10-31kg
21. The relation for paschen series is given as:
a. 1/λ = RH (1/22 – 1/n2)
b. 1/λ = RH (1/32 – 1/n2)
c. 1/λ = RH (1/42 – 1/n2)
d. 1/λ = RH (1/52 – 1/n2)
22. Which of the following series of hydrogen spectrum lies in ultra violet region?
a. Paschen series
b. Lyman series
c. Bracket series
d. Balmar series
23. A device used to detect very weak magnetic field produced by brain is named as:
a. Squid
b. MRI
c. CRO
d. CAT scans
24. k oc – x rays are produces due to transition of electrons from:
a. M to K shell
b. K to L shell
c. M to L shell
d. L to K shell
25. Hydrogen atom spectrum does not lie in:
a. Infrared region
b. Ultraviolet region
c. X-rays region
d. Visible region