Blackbody Radiation

What is spectral energy density?

What does the spectral density tell us?

What is spectral density of radiation?

What is the difference between energy spectral density and power spectral density?

Why energy spectral density is important?

What is the formula for emissive power?

Is absorptive power and emissivity same?

What is the spectral absorptive power?

Find the amount of energy transmitted if, $150 \mathrm{J}$ of energy is incident on area $2 {\mathrm{m}}^2$. Given $Q_r= 15 \mathrm{J}$ and coefficient of absorption is $0.6$.

Half part of ice block is covered with black cloth and rest half is covered with white cloth and then it is kept in sunlight. After some time clothes are removed to see the melted ice. Which of the following statements is correct ?

Heat radiations propagate with the speed of

Scientists have made a light source whose spectral emissive power $\frac{dI}{d\lambda }$ is constant over the visible range. Here $I$ is intensity and $\lambda$ is the wavelength. In other words, $\frac{dI}{d\lambda }$ graph is shown below. This beam of area $1 {\mathrm{m}}^2$ is incident on the emitter plate of the photoelectric tube. The collector plate is sufficiently positive so that tube is in saturation mode. Assume that each capable photon liberates $1$ electron. If work function is $2 \mathrm{eV},$ what is the current (in $\mathrm{A}$) in the tube? Round off to the nearest integer.

Scientists have made a light source whose spectral emissive power $\frac{dI}{d\lambda }$ is constant over the visible range. Here $I$ is intensity and $\lambda$ is the wavelength. In other words, $\frac{dI}{d\lambda }$ graph is shown below. This beam of area $1 {\mathrm{m}}^2$ is incident on the emitter plate of the photoelectric tube. The collector plate is sufficiently positive so that tube is in saturation mode. Assume that each capable photon liberates $1$ electron. If work function is $2 \mathrm{eV},$ what is the current (in $\mathrm{A}$) in the tube? Round off to the nearest integer.

Which of the following statement is correct

No medium is required for transfer of heat by the process of thermal _____.

Three large identical plates are kept parallel to each other. The outer two plates are maintained at temperatures $T$ and $2T$, respectively. The temperature of the middle plate in steady state will be close to

A solid copper sphere ($e=1$, density $\rho$ and specific heat capacity $c$) of radius $r$ at an initial temperature $200 \mathrm{K}$ is suspended inside a chamber whose walls are at almost $0 \mathrm{K}$. The time required (in $\mu s$) for the temperature of the sphere to drop to $100 \mathrm{K}$ is $\frac{n}{72}\frac{r\rho c}{\sigma }$. Find the value of $n$. (All symbols have their usual meaning)

The spectra of a black body at temperature $327 °\mathrm{C}$ and $627 °\mathrm{C}$ are shown in figure. If $A_{1 }$ and $A_2$ be the areas under the two curves respectively, the value of $A_2/A_1$ is :-

A good absorber is

Find the amount of energy transmitted, if $150 \mathrm{J}$ of energy is incident on area of $2 {\mathrm{m}}^2$. Given $Q_r= 15 \mathrm{J}$ and coefficient of absorption is $0.6$.