List of top Physics Questions

Show that the nuclear density is independent of mass number.
How is the necessary force provided to an electron to keep it moving in a circular orbit according to Bohr model of hydrogen atom? Derive an expression for the total energy of an electron moving in an orbit of radius \( r \) in hydrogen atom. Give the significance of the negative sign in this expression.
A rectangular loop carries a current of 1 A. A straight long wire carrying 2 A current is kept near the loop in the same plane as shown in the figure.
rectangular loop carries a current of 1 A.
Find:
(i) the torque acting on the loop, and
(ii) the magnitude and direction of the net force on the loop.
Name the electromagnetic wave used (i) in radar, (ii) in eye surgery, and (iii) as a diagnostic tool in medicine. Write their wavelength range also.
In an n-type semiconductor, electron-hole combination is a continuous process at room temperature. Yet the electron concentration is always greater than the hole concentration in it. Explain.
Draw a ray diagram showing the image formation when a concave mirror produces a real, inverted, and magnified image of an object and hence obtain the mirror formula.
Two cells of EMFs \( E_1 \) and \( E_2 \), and internal resistances \( r_1 \) and \( r_2 \), are connected in parallel. Derive an expression for the EMF and internal resistance of the equivalent cell.
Define ‘self-inductance’ of a coil. Derive an expression for self-inductance of a long solenoid of cross-sectional area \( A \) and length \( l \), having \( n \) turns per unit length.
A right-angled isosceles glass prism ABC is kept in contact with an equilateral triangular prism DBC as shown in the figure. Both prisms are made of the same glass of refractive index 1.6. Trace the path of the ray MN incident normally on face AB as it passes through the combination.
right-angled isosceles glass prism
Two statements are given one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer from the codes (A), (B), (C) and (D) as given below.
Assertion (A): The binding energy per nucleon is practically constant for mass number in the range \( 30<A<170 \).
Reason (R): Nuclear forces between the nucleons for mass numbers in the range \( 30<A<170 \) are not short-range.
A point source of light in air is kept at a distance of 12 cm in front of a convex spherical surface of glass of refractive index 1.5 and radius of curvature 30 cm. Find the nature and position of the image formed.
Find the equivalent resistance between points A and B for the network shown in the figure.
equivalent resistance between points A and B
Find the intensity at a point on the screen in Young’s double slit experiment, at which the interfering waves of intensity \( I_0 \) each, have a path difference of (i) \( \frac{\lambda}{3} \), and (ii) \( \frac{\lambda}{2} \).
A laser beam of frequency \( 3.0 \times 10^{14} \) Hz produces average power of 9 mW. Find (i) the energy of a photon of the beam, and (ii) the number of photons emitted per second on an average by the source.
The momentum (in kg·m/s) of a photon of frequency \( 6.0 \times 10^{14} \) Hz is:
Two statements are given one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer from the codes (A), (B), (C) and (D) as given below.
Assertion (A): X-rays are produced when slow moving electrons are stopped by a metal target of high atomic number.
Reason (R): X-rays consist of low-energy photons.
Inside a nucleus, the nuclear forces between proton and proton, proton and neutron, neutron and neutron are \( F_{pp} \), \( F_{pn} \), and \( F_{nn} \) respectively. Then:
Two statements are given one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer from the codes (A), (B), (C) and (D) as given below.
Assertion (A): A hole is an apparent free particle with effective positive electronic charge.
Reason (R): A hole is not necessarily a vacancy left behind by an electron in the valence band.
Two statements are given one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer from the codes (A), (B), (C) and (D) as given below.
Assertion (A): In a reflecting telescope, the image does not have chromatic aberration.
Reason (R): Chromatic aberration occurs only due to refraction of light through an optical medium.
The work function of a material is 2.21 eV. Which of the following cannot produce photoelectrons from it?
Two coherent waves, each of intensity \( I_0 \), produce interference pattern on a screen. The average intensity of light on the screen is:
A piece of a diamagnetic material, free to move when placed in a uniform magnetic field:
An AC source is connected to a resistor and an inductor in series. The voltage across the resistor and inductor are 8 V and 6 V respectively. The voltage of the source is:
A galvanometer can be converted into an ammeter of desired range by connecting a:
A vertically held bar magnet is dropped along the axis of a copper ring having a cut as shown in the diagram. The acceleration of the falling magnet is:
vertically held bar magnet is dropped along the axis of a copper ring