Physics Test - ...

The three stable isotopes of neon: \({ }^{20} \mathrm{Ne}_{10},{ }^{21} \mathrm{Ne}_{10}\) and \({ }^{22} \mathrm{Ne}_{10}\) have respective abundances of \(90.51 \%, 0.27 \%\) and \(9.22 \%\). The atomic masses of the three isotopes are \(19.99 \mathrm{~u}, 20.99 \mathrm{~u}\) and \(21.99 \mathrm{~u}\), respectively. Obtain the average atomic mass of neon.

The temperature determines the direction of net change of:

Displacement of a particle executing simple harmonic motion is represented by \(\mathrm{Y}=\) \(0.08 \sin \left(3 \pi \mathrm{t}+\frac{\pi}{4}\right)\) metre. Then calculate:

(a) Time period.

(b) Initial phase

(c) Displacement from mean position at \(\mathrm{t}=\frac{7}{36}\) sec.

A non monochromatic light is used in an experiment on photoelectric effect. The stopping potential: 

Two stable isotopes of lithium \(^6 Li_3\) and \(^7 Li_3\) have respective abundances of \(7.5 \%\) and \(92.5 \%\). These isotopes have masses \(6.01512 \mathrm{~u}\) and \(7.01600 \mathrm{u}\), respectively. Find the atomic mass of lithium.

The farther away a planet is from the Sun:

Light rays from an object fall on a surface and get reflected in a completely diffused manner. What can you say about the nature of image of the object?

Which of the following pairs has the same dimensions?

A Carnot engine, whose efficiency is 40%, takes in heat from a source maintained at a temperature of 500K. It is desired to have an engine of efficiency 60%. Then, the intake temperature for the same exhaust (sink) temperature must be :

A p-n junction has acceptor impurity concentration of \(10^{17} \mathrm{~cm}^{-3}\) in the \(P\) side and donor impurity concentration of \(10^{16}\) \(\mathrm{cm}^{-3}\) in the \(N\) side. What is the contact potential at the junction?

\((k T=\) thermal energy, intrinsic carrier concentration \(\left.n_{\mathrm{i}}=1.6 \times 10^{10} \mathrm{~cm}^{-3}\right)\)