### NEET Physics - New - Dual Nature of Matter and Radiation

#### Question - 1

An electron of mass m with an initial velocity v = v0i(v0 > 0) enters in electric field E = - E0î (E0 = constant > 0). If λ0 is its de-Broglie wavelength initially, then its de Broglie wavelength at time t is :

• A λ0 /[1 + (eE0/mv0) x t]
• B λ0[1 + (eE0/mv0) x t]
• C λ0t
• D λ0

#### Question - 2

When the light of frequency 2v0 (where v0 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 5v0, the maximum velocity of electrons emitted from the same plate is v2. The ratio of v1 to v2 is :

• A 1 : 2
• B 1 : 4
• C 4 : 1
• D 2 : 1

#### Question - 3

The de Broglie wavelength of a neutron in thermal equilibrium with heavy water at a temperature T (Kelvin) and mass m, is :

• A $h/\sqrt { 3mkT }$
• B $2h/\sqrt { 3mkT }$
• C $2h/\sqrt { mkT }$
• D $h/\sqrt { mkT }$

#### Question - 4

Photons with energy 5 eV are incident on a cathode C in a photoelectric cell. The maximum energy of emitted photoelectrons is 2 eV. When photons of energy 6 eV are incident on C, no photoelectrons will reach the anode A, if the stopping potential of A relative to C is :

• A + 3 V
• B + 4 V
• C - 1 V
• D - 3 V

#### Question - 5

A certain metallic surface is illuminated with monochromatic light of wavelength, λ. The stopping potential for photoelectric current for this light is 3V0. If the same surface is illuminated with light of wavelength 2λ, the stopping potential is V0. The threshold wavelength for this surface for photoelectric effect is :

• A  λ/4
• B  λ/6
• C
• D

#### Question - 6

When the energy of the incident radiation is increased by 20% the kinetic energy of the photoelectrons emitted from a metal surface increased from 0.5 eV to 0.8 eV. The work function of the metal is :

• A 1.3 eV
• B 1.5 eV
• C 0.65 eV
• D 1.0 eV

#### Question - 7

If the kinetic energy of the particle is increased to 16 times its previous value, the percentage change in the de Broglie wavelength of the particle is :

• A 60
• B 50
• C 25
• D 75

#### Question - 8

A piece of iron is heated in a flame. It first becomes dull red then becomes reddish yellow and finally turns to white hot. The correct explanation for the above observation is possible by using :

• A Stefan's law
• B Wien's displacement law
• C Kirchhoff's law
• D Newton's law of cooling

#### Question - 9

For photoelectric emission from certain metal the cutoff frequency is v. If radiation of frequency 2v impinges on the metal plate, the maximum possible velocity of the emitted electron will be (m is electron mass) :

• A $\sqrt { hv/(2m) }$
• B $\sqrt { hv/(m) }$
• C $\sqrt { 2hv/(m) }$
• D $2\sqrt { hv/(m) }$

#### Question - 10

Two radiations of photons energies 1 eV and 2.5 eV, successively illuminate a photosensitive metallic surface of work function 0.5 eV. The ratio of the maximum speeds of the emitted electrons is :

• A 1 : 2
• B 1 : 1
• C 1 : 5
• D 1 : 4