If mean wavelength of light radiated by 100 W lamp is 5000 Å , then number of photons radiated per

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11.Dual Nature of Radiation and matter

medium

If mean wavelength of light radiated by $100 W$ lamp is $5000 \mathring A$, then number of photons radiated per second are

A$3 \times {10^{23}}$

B$2.5 \times {10^{22}}$

C$2.5 \times {10^{20}}$

D$5 \times {10^{17}}$

Solution

(c) $P = \frac{{nhc}}{{\lambda t}} $
$\Rightarrow \frac{n}{t} = \frac{{P.\lambda }}{{hc}} = \frac{{100 \times 5000 \times {{10}^{ – 10}}}}{{6.6 \times {{10}^{ – 34}} \times 3 \times {{10}^8}}}$
$ = 2.50 \times {10^{20}}$

Standard 12

Physics

The beam of light has three wavelengths $4144 \,\mathring A$, $4972 \;\mathring A$ and $6216\; \mathring A$ with a total intensity of $3.6 \times$ $10^{-5}\,Wm ^2$ equally distributed amongst the three wavelengths. The beam falls normally on the area $1\,cm ^2$ of a clean metallic surface of work function $2.3\,eV$. Assume that there is no loss of light by reflection and that each energetically capable photon ejects one electron. Calculate the number of photoelectrons liberated in $2\,s$.

medium

Assertion : Photoelectric saturation current increases with the increase in frequency of incident light.
Reason : Energy of incident photons increases with increase in frequency and as a result photoelectric current increases.

easy

(AIIMS-2015)

Match the column

$(A)$ Hallwachs $\&$ Lenard $(P)$ Transformers

$(B)$ Franck-Hertz $(Q)$ Microwave

$(C)$ Klystron valve $(R)$ Quantization of energy levels

$(D)$ Nicola Tesla $(S)$ Photoelectric effect

medium

A radio transmitter operates at a frequency of $880 \,kHz$ and a power of $10\,kW$. The number of photons emitted per second are

easy

(AIPMT-1990)

If a source of power $4\,kW$ produces $10^{20}$ photons/second, the radiation belongs to a part of the spectrum called

medium

$(A)$ Hallwachs $\&$ Lenard	$(P)$ Transformers
$(B)$ Franck-Hertz	$(Q)$ Microwave
$(C)$ Klystron valve	$(R)$ Quantization of energy levels
$(D)$ Nicola Tesla	$(S)$ Photoelectric effect

If mean wavelength of light radiated by $100 W$ lamp is $5000 \mathring A$, then number of photons radiated per second are

Solution

Similar Questions

Assertion : Photoelectric saturation current increases with the increase in frequency of incident light. Reason : Energy of incident photons increases with increase in frequency and as a result photoelectric current increases.

Match the column $(A)$ Hallwachs $\&$ Lenard $(P)$ Transformers $(B)$ Franck-Hertz $(Q)$ Microwave $(C)$ Klystron valve $(R)$ Quantization of energy levels $(D)$ Nicola Tesla $(S)$ Photoelectric effect

A radio transmitter operates at a frequency of $880 \,kHz$ and a power of $10\,kW$. The number of photons emitted per second are

If a source of power $4\,kW$ produces $10^{20}$ photons/second, the radiation belongs to a part of the spectrum called

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Assertion : Photoelectric saturation current increases with the increase in frequency of incident light.
Reason : Energy of incident photons increases with increase in frequency and as a result photoelectric current increases.

Match the column

$(A)$ Hallwachs $\&$ Lenard $(P)$ Transformers

$(B)$ Franck-Hertz $(Q)$ Microwave

$(C)$ Klystron valve $(R)$ Quantization of energy levels

$(D)$ Nicola Tesla $(S)$ Photoelectric effect