Physics M.C.Q (1 Marks)

In producing X-rays a beam of electrons accelerated by a potential difference V is made to strike a metal target. For what value of V, X-rays will have the lowest wavelength of 0.3094 Å (a) 10 kV(b) 20 kV(c) 30 kV (d) 40 kV

The value of stopping potential in the following diagram

The correct graph between the maximum energy of a photoelectron and the inverse of wavelength of the incident radiation is given by the curve

The electrons are emitted in the photoelectric effect from a metal surface          (a) Only if the frequency of the incident radiation is above a certain threshold value(b) Only if the temperature of the surface is high(c) At a rate that is independent of the nature of the metal(d) With a maximum velocity proportional to the frequency of the incident radiation

Assertion :   The threshold frequency of photoelectric effect supports the particle nature of sunlight.
Reason      : If frequency of incident light is less than the threshold frequency, electrons are not emitted from metal surface.(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.(c) If assertion is true but reason is false.(d) If the assertion and reason both are false.

Assertion   :   Photoelectric effect demonstrates the wave nature of light.
Reason       : The number of photoelectrons is proportional to the frequency of light.(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.(c) If assertion is true but reason is false.(d) If the assertion and reason both are false.

Which of the following statements is correct(a) The current in a photocell increases with increasing frequency of light(b) The photocurrent is proportional to applied voltage(c) The photocurrent increases with increasing intensity of  light(d) The stopping potential increases with increasing intensity of incident light

When a point source of monochromatic light is at a distance of 0.2 m from a photoelectric cell, the cut-off voltage and the saturation current are 0.6 volt and 18 mA respectively. If the same source is placed 0.6 m away from the photoelectric cell, then(a) The stopping potential will be 0.2 V(b) The stopping potential will be 0.6 V(c) The saturation current will be 6 mA(d) The saturation current will be 18 mA

Stopping potential for photoelectrons(a) Does not depend on the frequency of the incident light(b) Does not depend upon the nature of the cathode material(c) Depends on both the frequency of the incident light and nature of the cathode material(d) Depends upon the intensity of the incident light

What determines the hardness of the X-rays obtained from the Coolige tube(a) Current in the filament(b) Pressure of air in the tube(c) Nature of target(d) Potential difference between cathode and target

According to Mosley's law, the frequency of a spectral line in X-ray spectrum varies as(a) Atomic number of the element(b) Square of the atomic number of the element(c) Square root of the atomic number of the element(d) Fourth power of the atomic number of the element

An electron beam in an X-ray tube is accelerated through a potential difference of 50000 volts. These are then made to fall on a tungsten target. The shortest wavelength of the X-ray emitted by the tube is(a) 2.5 Å (b) 0.25 nm(c) 0.25 cm(d) 0.025 nm

The structure of solid crystals is investigated by using (a) Cosmic rays(b) X-rays(c) Infrared radiations(d) γ -  rays

X-rays region lies between(a) Short radiowave and visible region(b) Visible and ultraviolet region(c) Gamma rays and ultraviolet region(d) Short radiowave and long radiowave

X-rays are produced due to (a) Break up of molecules          (b) Changing in atomic energy level(c) Changing in nuclear energy level(d) Radioactive disintegration

X-rays of which of the following wavelengths are hardest (a) 4 Å(b) 1 Å(c) 0.1 Å  (d) 2 Å

X-rays are known to be electromagnetic radiations. Therefore the X-ray photon has (a) Electric charge(b) Magnetic moment(c) Both electric charge and magnetic moment(d) Neither electric charge nor magnetic moment

Which of the following is accompanied by the characteristic X-ray emission          (a) α -  particle emission(b) Electron emission(c) Positron emission(d) K–electron capture

Bragg’s law for X-rays is (a) d sin θ = 2n λ (b) 2dsin θ = n λ (c) n sin θ = 2 λ d (d) None of these

The potential difference applied to an X-ray tube is increased. As a result, in the emitted radiation(a) The intensity increases(b) The minimum wavelength increases(c) The intensity decreases(d) The minimum wavelength decreases

X-rays can be used to study crystal structure, if the wavelength lies in the range(a) 2 Å to 0.1 Å(b) 10 Å to 5 Å(c) 50 Å to 10 Å(d) 100 Å to 50 Å

From the figure describing photoelectric effect we may infer correctly that         

According to Einstein's photoelectric equation, the graph between the kinetic energy of photoelectrons ejected and the frequency of incident radiation is