A 5 W source emits monochromatic light of wavelength 5000 A. When placed 0.5 m away, it liberates photoelectrons from a photosensitive metallic surface. when the source si moved to a distance of 1.0 m, the number of photoelectrons liberated will be reduced by a factor of:

4

8

16

2

Solution

The intensity of light is inversely proportional to the square of the distance.
$straight I space proportional to space 1 over straight r squared straight I subscript 1 over straight I subscript 2 space equals space fraction numerator left parenthesis straight r subscript 1 right parenthesis squared over denominator left parenthesis straight r subscript 2 right parenthesis squared end fraction Given space comma space straight r subscript 1 space equals space 0.5 space straight m comma space straight r subscript 2 space equals space 1.0 space straight m therefore comma straight I subscript 2 over straight I subscript 1 space equals space fraction numerator left parenthesis 0.5 right parenthesis squared over denominator left parenthesis 1 right parenthesis squared end fraction space equals space 1 fourth$
Now, since number of photoelectric emitted per second is directly proportional intensity, so number of electrons emitted would decrease by factor of 4.

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Wave Optics

A 5 W source emits monochromatic light of wavelength 5000 A. When placed 0.5 m away, it liberates photoelectrons from a photosensitive metallic surface. when the source si moved to a distance of 1.0 m, the number of photoelectrons liberated will be reduced by a factor of:

4

8

16

2

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Wave Optics

A 5 W source emits monochromatic light of wavelength 5000 A. When placed 0.5 m away, it liberates photoelectrons from a photosensitive metallic surface. when the source si moved to a distance of 1.0 m, the number of photoelectrons liberated will be reduced by a factor of: 4 8 16 2

Some More Questions From Wave Optics Chapter

Mock Test Series

NCERT Sample Papers

Entrance Exams Preparation

A 5 W source emits monochromatic light of wavelength 5000 A. When placed 0.5 m away, it liberates photoelectrons from a photosensitive metallic surface. when the source si moved to a distance of 1.0 m, the number of photoelectrons liberated will be reduced by a factor of:

4

8

16

2