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Physics - Modern Physics Question with Solution | TestHub

PhysicsModern PhysicsPhotoelectric effectHard2 minPYQ_2007

PhysicsHardsingle choice

A 5 watt source emits monochromatic light of wavelength $5000 \overset{˚}{A}$ . When placed $0.5 m$ away, it liberates photoclectrons from a photosensitive metallic surface. When the source is moved to a distance of $1.0 m$ , the number of photoelectrons liberated will be reduced by a factor of :NEET 2007

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Answer:

Solution:

Intensity is given by $I = \frac{p}{4 π d ^{2}}$ where $p =$ power of source $d =$ distance We know (assume) that light to spread out uniformly is all direction i.e. spherical source. $∴ I \propto \frac{1}{d ^{2}} or \frac{I _{1}}{I _{2}} = \frac{d _{2}^{2}}{d _{1}^{2}} or \frac{I _{1}}{I _{2}} = (\frac{1}{0.5})^{2} \Rightarrow \frac{I _{1}}{I _{2}} = 4 or I_{2} = \frac{I _{1}}{4}$

Stream:NEETSubject:PhysicsTopic:Modern PhysicsSubtopic:Photoelectric effect

⏱ 2mℹ️ Source: PYQ_2007

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