Dual Nature of Radiation and Matter · Question 26

A monochromatic source of light operating at 15 kW emits 2.5 1022 photons/s. The region of an electromagnetic spectrum to which the emitted electromagnetic radiation belongs to . (Take h=6.6 10-34 J.s and c=3 108 m/s).

1. Microwave
2. Infrared
3. Visible
4. Ultraviolet

K1 and K2 be the maximum kinetic energies of photoelectrons emitted from a surface of a given material for the light of wavelength 1 and 2, respectively. If 1=2 2 then the work function of material is given by :

1. K2+2K1
2. 2K2-K1
3. K1-2K2
4. K2-2K1

The de Broglie wavelength for an electron accelerated through the potential difference of V1 volt is 1. When the potential difference is changed to V2 volt, the associated de Broglie wavelength is increased by 50%. If (V1/V2 )= (9/ ), then the value of is .

An electron of mass m is moving in an electric field E=-2E0 i (E0 = constant > 0), with an initial velocity V=v0 i (v0 = constant > 0). If 0= h4mv0, its de Broglie wavelength at time t is . (e = charge of electron)

1. 4 0 [1- E0e2m tv0 ]
2. 4 0 [1+ E0e2m tv0 ]
3. 4 0 [1+ 2E0em tv0 ]
4. 4 0 [1- 2E0em tv0 ]

Light source having wavelength 331 nm is used to generate photo-electrons whose stopping potential is 0.2 V. The work function of the used metal in the experiment is 10-19 J. The value of is . (h=6.62 10-34 J s, e=1.6 10-19 C and c=3 108 m/s)

1. 3.68
2. 4.68
3. 5.68
4. 2.68

An electron is travelling with a velocity v in free space and when it enters a medium, its velocity is reduced by 20%. The de Broglie wavelength of electron in the medium is 0, where 0 is its de Broglie wavelength in free space. The value of is .

1. 1.20
2. 1.0
3. 1.25
4. 0.75

The graph shows variation of stopping potential V0 with the frequency of the incident radiation for three photosensitive metals X1, X2 and X3. Which metal will give out electrons with greater kinetic energy, for the same wavelength of incident radiation? [figure]

1. X1
2. X2
3. X3
4. All the metals will give out photoelectrons with same kinetic energies.

Match the List-I with List-II Choose the correct answer from the options given below :

1. A-III, B-IV, C-I, D-II
2. A-I, B-II, C-III, D-IV
3. A-IV, B-III, C-I, D-II
4. A-I, B-IV, C-III, D-II

The de Broglie wavelength associated with an electron accelerated through a potential difference V is e and the de Broglie wavelength associated with a proton accelerated through the same potential difference is p. If their corresponding masses are me and mp, respectively, then the ratio of their de Broglie wavelengths ( e p ) is .

1. mpme
2. memp
3. mpme
4. ( mpme )2

For a certain metal, when monochromatic light of wavelength is incident, the stopping potential for photoelectrons is 3V0. When the same metal is illuminated by light of wavelength 2 , then the stopping potential becomes V0. The threshold wavelength for photoelectric emission for the given metal is . The value of is .

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