Threshold Frequency

Q. temperature of black body is 3000 K. When black body gets cooled down then change in wavelength is (delta lambda = 9 micron) corresponding to maximum energy density. Now temperature of black body is- (1) 300K (2) 2700K (3) 270K (4) 1800K

Q. What would be the sign convention for work done on a system for a cylinder containing one mole of an ideal gas where Pext=Pint?

Q. if the temperature of the body is from 27 to 97 degree celcius then wavelength corresponding to maximum intensity become

Q. Work function of a metal is 2.51 eV. Its threshold frequency is

1. $5.9\times {10}^{14}Cycle/sec$.
2. $6.5\times {10}^{14}Cycle/sec$.
3. $9.4\times {10}^{14}Cycle/sec$.
4. $6.8\times {10}^{14}Cycle/sec$.

Q. In the experiment on photoelectric effect, the graph between $E_{max}$ and $v$ is found to be straight line as shown in figure.

The threshold frequency and Planck's constant according to this graph are

1. $3.33\times {10}^{18}{s}^{-1},6\times {10}^{-34}Js$
2. $6\times {10}^{18}{s}^{-1},6\times {10}^{-34}Js$
3. $2.66\times {10}^{18}{s}^{-1},4\times {10}^{-34}Js$
4. $4\times {10}^{18}{s}^{-1},3\times {10}^{-34}Js$

Q. Work energy theorem

Q. When one electron is taken towards the other electron, then the electric potential energy of the system

1. Decreases
2. Increases
3. Remains unchanged
4. Becomes zero

Q. A piano wire weighing 6⋅00 g and having a length of 90⋅0 cm emits a fundamental frequency corresponding to the "Middle C" $\left(\nu =261·63\mathrm{Hz}\right)$. Find the tension in the wire.

Q.

Statement 1: It was surprising for the scientist to observe that photocurrent depends on the frequency of the light.

Statement 2: According to the wave model , Energy of the light falling on the plate depends only on the amplitude of Light and not on frequency , so they assumed that changing frequency shouldn't change anything.

1. Statement 1 is true but statement 2 is not the correct reason for it

2. statement 1 is true and statement 2 is the correct reason for it.

3. Statement 1 and 2 both are false.

4. Statement 1 is true but statement 2 is false.

Q. The work function of a metal is $h{\nu }_0$. Light of frequency $\nu$ falls on this metal. The photoelectric effect will take place only if $\nu$ ${\nu }_0$.

1. $\ge$
2. $\le$
3. $>$
4. $<$

Q.

The work function for metals A, B and C are respectively 1.92 eV, 2.0 eV and 5 eV. According to Einstein’s equation, the metals which will emit photo electrons for a radiation of wavelength $4100\stackrel{\circ }{A}$ is/are

1. None of these

2. A only

3. A and B only

4. All the three metals

Q. why work is not done on or by the gas in case of isochoric process?