Assertion (A): In photo electric effect, photo electrons come out from inner orbits of atom.
Reason (R): Free electrons of the metal can not absorb energy of a photon.
Assertion (A) is false: Photoelectrons are ejected from the surface of the metal, not inner orbits. Reason (R) is false: Free electrons absorb photon energy to be ejected. Both statements are false.
Assertion (A): In photoelectric effect, on increasing the intensity of light, both the number of electrons emitted and kinetic energy of each of them get increased but photoelectric current remains unchanged.
Reason (R): The photoelectric current depends only on wavelength of light.
Assertion (A) is false: Increasing intensity increases number of electrons and current, but KE remains same. Reason (R) is false: Photoelectric current depends on intensity and frequency. Both statements are false.
Assertion (A): The smaller the wavelength of a photon, the more energy it has.
Reason (R): The smaller the wavelength of a photon, the less momentum it has.
Assertion (A) is true: Energy \(E = hc/\lambda\), so smaller \(\lambda\) means more energy. Reason (R) is false: Momentum \(p = h/\lambda\), so smaller \(\lambda\) means more momentum. (A) is true, (R) is false.
Assertion (A): An electron microscope is based on de Broglie’s hypothesis of matter waves.
Reason (R): Higher the accelerating potential, smaller is the de Broglie wavelength of the electron.
Assertion (A) is true: Electron microscopes utilize the wave nature of electrons. Reason (R) is true: de Broglie wavelength \(\lambda = h/\sqrt{2meV}\) decreases with higher potential (V). R explains A, as smaller wavelength allows better resolution.
Assertion (A): Photons do not carry momentum
Reason (R): A photon is a material particle.
Assertion (A) is false: Photons carry momentum \(p = E/c = h/\lambda\). Reason (R) is false: A photon is a quantum of light/energy, not a classical material particle. Both statements are false.
Assertion (A): Increase in intensity of light increases the kinetic energy of photoelectrons.
Reason (R): At stopping potential, no current flows in the circuit.
Assertion (A) is false: Kinetic energy of photoelectrons depends on frequency, not intensity. Reason (R) is true: Stopping potential is the reverse potential that stops all photocurrent. As (A) is false, option (4) is chosen by elimination.
Assertion (A): Kinetic energy of photoelectrons emitted by a photosensitive surface depends upon the intensity of incident photon.
Reason (R): The ejection of electrons from metallic surface is possible with frequency of incident photon below the threshold frequency.
Kinetic energy of photoelectrons depends on the frequency of incident light, not its intensity. Photoelectric emission requires the incident photon's frequency to be above the threshold frequency \(\nu_0\). Thus, both assertion (A) and reason (R) are false.
Assertion (A): Photoelectrons have a range of kinetic energy.
Reason (R): The work function varies as a function of depth from the surface.
Photoelectrons exhibit a range of kinetic energies because electrons lose varying amounts of energy while escaping the material. The work function (\phi\) is a constant for a given surface and does not vary with depth. Thus, assertion (A) is true, but reason (R) is false.
Assertion (A): Photoelectric effect demonstrates the wave nature of light.
Reason (R): The number of photoelectrons is proportional to the frequency of light.
The photoelectric effect experimentally supports the particle (photon) nature of light, not its wave nature. The number of photoelectrons emitted is directly proportional to the intensity of incident light, not its frequency. Therefore, both assertion (A) and reason (R) are false.
Assertion (A): On increasing the frequency of incident light, the photoelectric current increases.
Reason (R): Photoelectric current depends upon the wavelength of incident light.
Increasing the frequency of incident light increases the kinetic energy of emitted photoelectrons, not the photoelectric current. Photoelectric current depends primarily on the intensity of the incident light, provided the frequency is above the threshold. Therefore, both assertion (A) and reason (R) are false.