Dual Nature of Radiation and Matter

The light rays having photons of energy 4.2 eV are falling on a metal surface having a work function of 2.2 eV. The stopping potential of the surface is

1. 6.4 V
2. 2 eV
3. 2 V
4. 1.1 V

The threshold frequency of a photoelectric metal is 0. If light of frequency 4 0 is incident on this metal, then the maximum kinetic energy of emitted electrons will be :

1. 4h 0
2. h 0
3. 2h 0
4. 3h 0

The number of photons per second on an average emitted by the source of monochromatic light of wavelength 600 nm, when it delivers the power of 3.3 10-3 watt will be : (h = 6.6 10-34 J s)

1. 1015
2. 1018
3. 1017
4. 1016

An electromagnetic wave of wavelength ' ' is incident on a photosensitive surface of negligible work function. If 'm' mass is of photoelectron emitted from the surface has de-Broglie wavelength d, then :

1. = ( 2hmc ) d2
2. = ( 2mhc ) d2
3. d = ( 2mch ) 2
4. = ( 2mch ) d2

Light of frequency 1.5 times the threshold frequency is incident on a photosensitive material. What will be the photoelectric current if the frequency is halved and intensity is doubled?

1. four times
2. one-fourth
3. zero
4. doubled

The energy required to break one bond in DNA is 10-20 J. This value in eV is nearly :

1. 0.6
2. 0.06
3. 0.006
4. 6

An electron is accelerated from rest through a potential difference of V volt. If the de-Broglie wavelength of the electron is 1.227 10-2 nm, the potential difference is :

1. 102 V
2. 103 V
3. 104 V
4. 10 V

An electron is accelerated through a potential difference of 10,000 V. Its de Broglie wavelength is (nearly) : (me = 9 10-31 kg)

1. 12.2 10-12 m
2. 12.2 10-13 m
3. 12.2 10-14 m
4. 12.2 nm

An electron of mass m with an initial velocity v = v0 i (v0 > 0) enters an electric field E = -E0 i (E0 = constant > 0) at t = 0. If 0 is its de-Broglie wavelength initially, then its de-Broglie wavelength at time t is

1. 0 (1 + eE0mv0t )
2. 0 (1 + eE0mv0t )
3. 0t
4. 0

When the light of frequency 2 0 (where 0 is threshold frequency), is incident on a metal plate, the maximum velocity of electrons emitted is v1. When the frequency of the incident radiation is increased to 5 0, the maximum velocity of electrons emitted from the same plate is v2. The ratio of v1 to v2 is

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