Which of the following is true as regards photo emission? Velocity of emitted el

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Question
Which of the following is true as regards photo emission?
Options
A. Velocity of emitted electrons is dependent on light intensity
B. Rate of photo emission is inversely proportional to light intensity
C. Maximum velocity of electron increases with decreasing wave length
D. Both holes and electrons are produced

Correct Answer

Maximum velocity of electron increases with decreasing wave length

Explanation

As wavelength decreases, frequency increases and maximum velocity of electron increases.

Electronic Devices and Circuits problems

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1. The most commonly used semiconductor material is
Options
A. silicon
B. germanium
C. mixture of silicon and germanium
D. none of the above

2. In a p type material the Fermi level is 0.3 eV above valence band. The concentration of acceptor atoms is increased. The new position of Fermi level is likely to be
Options
A. 0.5 eV above valence band
B. 0.28 eV above valence band
C. 0.1 eV above valence band
D. below the valence band

3. As compared to an ordinary semiconductor diode, a Schottky diode
Options
A. has higher reverse saturation current
B. has higher reverse saturation current and higher cut in voltage
C. has higher reverse saturation current and lower cut in voltage
D. has lower reverse saturation current and lower cut in voltage

4. The minority carrier life time and diffusion constant in a semiconductor material are respectively 100 microsecond and 100 cm²/sec. The diffusion length is
Options
A. 0.1 cm
B. 0.01 cm
C. 0.0141 cm
D. 1 cm

5. Assertion (A): A p-n junction has high resistance in reverse direction.
Reason (R): When a reverse bias is applied to p-n junction, the width of depletion layer increases.
Options
A. Both A and R are true and R is correct explanation of A
B. Both A and R are true but R is not a correct explanation of A
C. A is true but R is false
D. A is false but R is true

8. In a 100 turn coil, if the flux through each turn is (t³ - 2t)mW_b, the magnitude of the induced emf in the coil at a time of 4 sec is
Options
A. 46 mV
B. 56 mV
C. 4.6 V
D. 5.6 V

9. Charge needed within a unit sphere centred at the origin for producing a potential field,
Options
A. 12 p_c
B. 60 p_c
C. 120 p_c
D. 180 p_c

10. A wave is propagated in a waveguide at frequency of 9 GHz and separation is 2 cm between walls Calculate group velocity for dominant mode.
Options
A. 1.8 x 10⁸ m/sec
B. 5 x 10⁸ m/sec
C. 3 x 10⁸ m/sec
D. 1.5 x 10⁸ m/sec

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