Question

Light of wavelength 3500 Å is incident on two metals A and B. Which metal will emit photoelectrons, if their work functions are 4.2 eV and 1.9 eV respectively? 

Solution

Correct option is

Metal B, 3.54 eV

The energy of incident light photon of wavelength

        

            is   

       

           

           

           

           

            = 3.54 eV. 

The incident light will yield photoelectrons if its energy is greater than the work function of the metal. Thus, metal B(W = 1.9 eV) will emit photoelectrons.  

SIMILAR QUESTIONS

Q1

Monochromatic light of frequency  is produced by a laser. The power emitted is . What is the energy of a photon in the light beam?

Q2

A beam of green light  gives energy at the rate of 1 Js–1 to a surface where it is fully absorbed. How many photons reach the surface per second? If every 100 photons emit one electron, how much current will flow from the surface? 

Q3

 

Calculate the number of photons emitted per second by a transmitter of 10 kW power, emitting radio waves of wavelength 500 m. 

Q4

Calculate the number of photons emitted per second by a transmitter of 10 kW power, emitting radio waves of wavelength 500 m. 

Q5

The minimum light intensity that can be perceived by human eye is about 10–10 Wm–2. Find the number of visible-light photons that must enter the pupil of our eye per second for vision. Take the area of the pupil to be about 0.4 cm2 and the average wavelength of visible light to be 5000 Å. 

Q6

A 5-W point-source emits monochromatic light of wavelength 5000 Å. How many photons per second strike a unit area placed 5 m away from the source and illuminated by it? What should be the work function of the metal from whose surface this light can liberate photoelectrons? 

  

Q7

The wavelength of a photon is 1.4 Å. It becomes 2.0 Å after a collision with an electron. Calculate the energy of the scattered electron. 

  

Q8

Find the moment and equivalent mass of a photon of radiation of wavelength 3300 Å. 

Q9

An isolated hydrogen atom emits a photon of energy 10.2 eV. Calculate momentum of the photon. 

Q10

A light beam of wavelength 6000 Å and intensity  falls normally on a photon-cathode of surface area 1 cm2 and work function 2 eV. Assuming that there is no loss of light by reflection etc., calculate the number of photoelectrons emitted per second.