Calculate the work function of sodium metal in electron-volt, if the photoelectric threshold wavelength is 5400 A o . Will photoelectrons be emitted, if red light of wavelength 6800 A o be incident on sodium?

The work function is defined as the energy required to eject electrons from the metal surface without imparting any kinetic energy to them. Given the threshold wavelength 5400 ° A Wave length of red light = 6800 ° A The energy of the incident radiations is , E = hν = hc λ = 6 . 63 × 10 - 19 × 3 × 10 8 5400 × 10 - 10 × 1 . 6 × 10 - 19 = 2 . 3 eV . As the given radiations ( 6800 ° A ) have more wave length, its energy will be less than the work function of the metal, hence the photo emission is not possible.

Calculate the work function of sodium metal in electron-volt, if the photoelectric threshold wavelength is 5400 A o . Will photoelectrons be emitted, if red light of wavelength 6800 A o be incident on sodium?

The work function is defined as the energy required to eject electrons from the metal surface without imparting any kinetic energy to them. Given the threshold wavelength 5400 ° A Wave length of red light = 6800 ° A The energy of the incident radiations is , E = hν = hc λ = 6 . 63 × 10 - 19 × 3 × 10 8 5400 × 10 - 10 × 1 . 6 × 10 - 19 = 2 . 3 eV . As the given radiations ( 6800 ° A ) have more wave length, its energy will be less than the work function of the metal, hence the photo emission is not possible.

A metal whose work function is 3 . 0 e V , is illuminated by light of wavelength 3 × 10 - 7 m . Calculate the threshold frequency. Take h = 6 . 62 × 10 - 34 JHz - 1

Work function is the minimum energy required to eject electron from the metal Given, the work function is 3 . 0 eV ,and the wavelength of light = 3 × 10 - 7 m the corresponding threshold frequency is related by the equation E = hν Substituting the given values ( i n eV ), we have, ν = E h = 3 . 0 × 1 . 6 × 10 - 19 6 . 62 × 10 - 34 = 7 . 3 × 10 14 Hz

A metal whose work function is 3 . 0 eV , is illuminated by light of wavelength 3 × 10 - 7 m . Calculate the maximum energy of photoelectrons.

Given The work function = 3 . 0 ev Wavelength of incident light= 3 × 10 7 m The work function is defined as the energy required to eject electrons from the metal surface without imparting any kinetic energy to them. The energy of the incident radiations is E = hν = hc λ = 6 . 62 × 10 - 34 × 3 × 10 8 3 . 0 × 10 - 7 × 1 . 6 × 10 - 19 = 4 . 14 eV According to Einstein's photoelectric equation, the maximum kinetic energy of the photoelectrons is given by K m a x = E - ϕ where ϕ is the work function of the metal. Substituting the values, we have, K max = 4 . 14 - 3 . 0 = 1 . 14 eV Hence the maximum energy of the photoelectrons is 1 . 14 eV .

A metal whose work function is 3 . 0 e V , is illuminated by light of wavelength 3 × 10 - 7 m . Calculate the stopping potential.

Given the work function ϕ = 3 . 0 V and wavelength of the incident radiation λ = 3 × 10 7 m The work function is defined as the energy required to eject electrons from the metal surface without imparting any kinetic energy to them. The energy of the incident radiations is E = hν = hc λ = 6 . 62 × 10 - 34 × 3 × 10 8 3 . 0 × 10 - 7 × 1 . 6 × 10 - 19 = 4 . 14 eV According to Einstein's photoelectric equation, the maximum kinetic energy of the photoelectrons is given by, K max = E - ϕ where ϕ is the work function of the metal. Substituting the values, we have, K max = 4 . 14 - 3 . 0 = 1 . 14 eV As the work function is equal to the voltage required to stop the photo electrons with the maximum KE, hence the stopping potential eV 0 = 1 . 14 eV or V 0 = 1 . 14 V Hence the work function is 1 . 14 V .

E M B I B E

ISC Physics Class 12, Part-2>Chapter 10 - Photoelectric Effect>QUESTIONS>Q 24

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Calculate the work function of sodium metal in electron-volt, if the photoelectric threshold wavelength is $5400 \overset{o}{A}$ . Will photoelectrons be emitted, if red light of wavelength $6800 \overset{o}{A}$ be incident on sodium?

Important Questions on Photoelectric Effect

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ISC Physics Class 12, Part-2>Chapter 10 - Photoelectric Effect>QUESTIONS>Q 25

The work function of a metal is $4.5 eV$ . Light of wavelength $2200 \overset{\circ}{A}$ is falling on the surface of this metal. Find the kinetic energy of the fastest photoelectrons emitted.

$(h = 4.13 \times 10^{- 15} eV s)$