Home
Class 12
PHYSICS
Ultraviolet light of wavelength 2271 Å f...

Ultraviolet light of wavelength 2271 Å fro a 100 W mercury source irradiates a photocell made of molybdenum metal. If the stopping potential is -1.3V, estimate the work function of the metal. How would the photocell respond to a high intensity `(~10^(5)Wm^(-2))` red light of wavelength 6328 Å produced bya He-Ne laser ?

Text Solution

Verified by Experts

Here `lamda=2271Å=2271xx10^(-10)m=2.271xx10^(-7)m`, and stopping potential `V_(0)=-1.3V`
Using Einstein.s photoelectronic equation `hv-phi_(0)=eV_(0)`, we have
`phi_(0)=hv-eV_(0)=(hc)/(lamda)-eV_(0)=(6.63xx10^(-34)xx3xx10^(8))/(2.271xx10^(-7))-1.3xx1.6xx10^(-19)J`
`=8.758xx10^(-19)-2.08xx10^(-19)J=6.678xx10^(-19)J=(6.678xx10^(-19))/(1.6xx10^(-19))eV=4.17eV`
For He-Ne laser light of wavelength `lamda.=6328Å=6.328xx10^(-7)m,` the enrgy of a photon will be
`E.=(hc)/(lamda.)=(6.63xx10^(-34)xx3xx10^(8))/(6.328xx10^(-7))J=(6.63xx10^(-34)xx3xx10^(8))/(6.328xx10^(-7)xx1.6xx10^(-19))eV=1.964eV`
As `E.ltphi_(0)`, hence no photoelectric emission will take place irrespective of intenstiy of laser beam.
Promotional Banner

Topper's Solved these Questions

  • DUAL NATURE OF RADIATION AND MATTER

    U-LIKE SERIES|Exercise CASE BASED/SOURCE-BASED INTEGRATED QUESTIONS|10 Videos

  • DUAL NATURE OF RADIATION AND MATTER

    U-LIKE SERIES|Exercise MULTIPLE CHOICE QUESTIONS|30 Videos

  • DUAL NATURE OF RADIATION AND MATTER

    U-LIKE SERIES|Exercise SELF ASSESSMENT TEST SECTION-C (VERY SHORT ANSWER QUESTIONS)|3 Videos

  • CURRENT ELECTRICITY

    U-LIKE SERIES|Exercise SELF ASSESSMENT TEST (SECTION C )|3 Videos

  • ELECTRIC CHARGES AND FIELDS

    U-LIKE SERIES|Exercise SELF ASSESSMENT TEST (SECTION-B) (VERY SHORT ANSWER QUESTIONS)|4 Videos

Similar Questions

Explore conceptually related problems

Ultraviolet light of wavelength 2271Å from a 100W mercury souce irradiates a photocell made of molybdenum metal. If the stopping potential is 1.3V, estimate the work function of the metal. How would the photocell respond to a high intensity (~10^(5)Wm^(-2)) red light of wave length 6328Å produced by a He-Ne laser?

An ultraviolet light of wavelength 2000 Å irradiates a photo cell made of molybdenum metal . If the stopping potential is -1.5 V , what is the work function of the metal ?

A low intensity ultraviolet light of wavelength 2271Å irradiates a photocell made of molybdenum metal. If the stopping potential is 1.3V, find the work function of the metal. Will the photocell work if it is irradiated by a high intensity red light of wavelength 6328Å ?

For intensity I of a light of wavelength 5000 Å the photoelectron saturation current is 0.40 mu A and stopping potential is 1.36 V , the work function of metal is

Amonochromatic light source of power 5mW emits 8 xx 10^15 photons per second. This light ejects photoelectrons from a metal surface. The stopping potential for this set up is 2V. Calculate the work function of the metal.

A monochromatic light source of intensity 5 m W emits (8x10^15) photons per second . This light ejects photoelectrons from a metal surface. The stopping potential for this setup is 2.0 V. Calculate the work function of the metal.

A photon of wavelength 1000 Å has energy 12.3 eV . If light of wavelength 5000 Å , having intensity I, falls on a metal surface, the saturaion current is 0.40 mu A and the stopping potential is 1.36 V . The work function of metal is

Light of wavelength 3320 Å incidents on metal surface (work function = 1.07 eV ). To stop emission of photo electron, retarding potential required to be -