The photoelectric cut-off voltage in a certain experiment is 1.5 V. What is the maximum kinetic energy of photoelectrons emitted?

$$\begin{gathered} \left(1\right) 2.1\times {10}^{-19} J \\ \left(2\right) 1.7\times {10}^{-19} J \\ \left(3\right) 2.4\times {10}^{-19} J \\ \left(4\right) 1.1\times {10}^{-19} J \end{gathered}$$

Monochromatic light of wavelength 632.8 nm is produced by a
helium-neon laser. The power emitted is 9.42 mW. The energy of each photon in the light beam is:

$$\begin{gathered} \left(1\right) 4.801\times {10}^{-19} J \\ \left(2\right) 2.121\times {10}^{-19} J \\ \left(3\right) 5.043\times {10}^{-19} J \\ \left(4\right) 3.141\times {10}^{-19} J \end{gathered}$$

The energy flux of sunlight reaching the surface of the earth is 1.388 × 10³ W/m². How many photons(nearly) per square meter are incident on the Earth per second? Assume an average wavelength of 550 nm.

(1) $3.84\times {10}^{21}$

(2) $2.97\times {10}^{21}$

(3) $4.12\times {10}^{21}$

(4) $2.10\times {10}^{21}$

In an experiment on the photoelectric effect, the slope of the cut-off voltage versus frequency of incident light is found to be $4.12\times {10}^{-15} V s$. The value of Planck's constant is:

(1) $6.682\times {10}^{-4} Js$

(2) $6.592\times {10}^{-34} Js$

(3) $6.621\times {10}^{-34} Js$

(4) $6.502\times {10}^{-4} Js$

A 100 W sodium lamp radiates energy uniformly in all directions. The lamp is located at the center of a large sphere that absorbs all the sodium light which is incident on it. The wavelength of sodium light is 589 nm. What is the energy per photon associated with the sodium light?

$$\begin{gathered} \left(1\right) 1.21 eV \\ \left(2\right) 2.21 eV \\ \left(3\right) 2.11 eV \\ \left(4\right) 1.11 eV \end{gathered}$$

Light of frequency $7.21\times {10}^{14} \mathrm{Hz}$ is incident on a metal surface. Electrons with a maximum speed of $6.0\times {10}^5 \mathrm{m}/\mathrm{s}$ are ejected from the surface. What is the threshold frequency for the photoemission of electrons?

$$\begin{gathered} \left(1\right) 5.109\times {10}^{14} Hz \\ \left(2\right) 3.345\times {10}^{14} Hz \\ \left(3\right) 6.733\times {10}^{14} Hz \\ \left(4\right) 4.738\times {10}^{14} Hz \end{gathered}$$

The threshold frequency for a certain metal is $3.3\times {10}^{14} \mathrm{Hz}.$ If the light of frequency $8.2\times {10}^{14} \mathrm{Hz}$ is incident on the metal, the cut-off voltage for the photoelectric emission is:

(1) 1.1210 V.

(2) 2.0292 V.

(3) 3.8651 V.

(4) 4.0832 V.

Light of intensity 10^-5 W m^-2 falls on a sodium photo-cell of surface area 2 cm². Assuming that the top 5 layers of sodium absorb the incident energy, The time required for photoelectric emission in the wave-picture of radiation is: (The work function for the metal is given to be about 2 eV.)

(1) 0.2 year

(2) 0.3 year

(3) 0.4 year

(4) 0.5 year 

Monochromatic radiation of wavelength 640.2 nm (1 nm = 10^-9 m) from a neon lamp irradiates photosensitive material made of cesium on tungsten. The stopping voltage is measured to be 0.54 V. The source is replaced by an iron source and its 427.2 nm line irradiates the same photo-cell. The new stopping voltage is:

(1) 0.54 eV

(2) 1.3 eV

(3) 1.5 eV

(4) 1.63 eV

Ultraviolet light of wavelength 2271 Å from a 100 W mercury source irradiates a photocell made of molybdenum metal. If the stopping potential is −1.3 V, the work function of the metal is:

(1) 4.15 eV

(2) 3.01 eV

(3) 1.30 eV

(4) 2.12 eV