WBJEE PRACTICE PAPER
1. Bohr's theory of hydrogen atom did not explain fully
A. diameter of H atom
B. emission spectra
C. ionisation energy
D. the fine structure of even hydrogen spectrum
2. A current loop placed in a non-uniform magnetic field experiences :
A. a force of repulsion
B. a force of attraction
C. a torque but not force
D. a force and a torque
3. For a heavily doped n-type semi-conductor, Fermi-level lies
A. a little below the conduction band
B. a little above the valence band
C. a little inside the valence band
D. at the centre of the band gap
4. Which of the following indicates that the galaxies are receding from us ?
A. Neutron Star
B. White dwarf
C. Black hole
D. Red shift
5. In a transistor, the relation between α and β is
A. β = α /(1 - α )
B. β = 1/(1 - α )
C. β = α /(1 + α )
D. β = 1 - α
6. Which of the following electro-magnetic rays has maximum wavelength?
A. Radio waves
B. X-rays
C. Infra-red rays
D. Ultra-violet rays
7. In a transistor
A. there is 1 p-n junction
B. there are 2 p-n junctions
C. there are 3 p-n junctions
D. none of these
8. Germanium is doped with arsenic, what will be the result ?
A. p-type semi-conductor
B. n-type semi-conductor
C. intrinsic semi-conductor
D. none of these
9. An electron is moving in 1st orbit. The factor nh/2π is
A. It's Angular momentum
B. Energy
C. Linear momentum
D. None of these
10. The energy of an electron is
A. hc/λ
B. hλ/c
C. hv/c
D. none of these
11. According to Bohr's Theory, electron moves around in those orbits only in which nh/2π is its
A. Impulse
B. Angular momentum
C. Force
D. Kinetic Energy
12. Which of the following waves can produce photo-electric effect?
A. Ultra-sound
B. Infra-red
C. Radio-waves
D. X-rays
14. If two lenses are kept coaxial together, then what will be their power?
A. R1 + R2
B. (R1 R2)/ (R1 + R2)
C. (R1 + R2)/(R1 R2)
D. none of these
15. The angular fringe-width does not depend upon
A. wavelength (λ )
B. distance between slits (d)
C. distance between slits and screen
(D) D. ratio (λ /d)
