The threshold wavelength for photoelectric em | vedclass

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Question

(D) For photoelectric emission to occur,the incident radiation must have a wavelength $\lambda$ less than or equal to the threshold wavelength $\lambd

Vedclass · Accepted Answer

$C$ and $D$ only

Vedclass · Answer

(D) For photoelectric emission to occur,the incident radiation must have a wavelength $\lambda$ less than or equal to the threshold wavelength $\lambda_0$.Given $\lambda_0 = 5500\,\mathring A$.Infra-red radiation has wavelengths greater than $7000\,\mathring A$,which is greater than $5500\,\mathring A$. Thus,it cannot cause photoelectric emission.Ultra-violet radiation has wavelengths typically between $100\,\mathring A$ and $4000\,\mathring A$,which is less than $5500\,\mathring A$. Thus,it can cause photoelectric emission regardless of the power of the lamp.Therefore,both the $75\,W$ and $10\,W$ ultra-violet lamps will cause emission.The correct option is $D$ ($C$ and $D$ only).

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