Q 1 :    

Average force exerted on a non-reflecting surface at normal incidence is $2.4\times {10}^{-4}N$. If 360 $W.C{m}^2$ is the light energy flux during span of 1 hour 30 minutes, Then the area of the surface is             [2024]

• $0.02$ $m^2$

   

• $0.2$ $m^2$

   

• $20$ $m^2$

   

• $0.1$ $m^2$

   

Q 2 :    

An object is placed in a medium of refractive index 3. An electromagnetic wave of intensity $6\times {10}^{8}W/m^2$ falls normally on the object and it is absorbed completely. The radiation pressure on the object would be (speed of light in free space $=3\times {10}^{8}m/s$)                 [2024]

• $36N{m}^{-2}$

   

• $18N{m}^{-2}$

   

• $6N{m}^{-2}$

   

• $2N{m}^{-2}$

   

Q 3 :    

Two sources of light emit with a power of 200 W. The ratio of the number of photons of visible light emitted by each source having wavelengths 300 nm and 500 nm respectively, will be               [2024]

• 3 : 5

   

• 1 : 5

   

• 5 : 3

   

• 1 : 3

   

Q 4 :    

Monochromatic light of frequency $6\times {10}^{14}Hz$ is produced by a laser. The power emitted is $2\times {10}^{-3}W$. How many photons per second, on an average, are emitted by the source?               [2024]

(Given $h=6.63\times {10}^{-34}$ Js)

• $9\times {10}^{18}$

   

• $6\times {10}^{15}$

   

• $5\times {10}^{15}$

   

• $7\times {10}^{16}$

   

Q 5 :    

In the Franck-Hertz experiment, the first dip in the current-voltage graph for hydrogen is observed at 10.2 V. The wavelength of light emitted by the hydrogen atom when excited to the first excitation level is ___ nm.

(Given $hc=1245eVnm, e=1.6\times {10}^{-19}C$)                [2024]