List of top Physics Questions

The ratio of the shortest wavelength of the Balmer series to the shortest wavelength of the Lyman series for the hydrogen atom is:
Which of the following transitions of He$^+$ ion will give rise to a spectral line that has the same wavelength as the spectral line in a hydrogen atom?

If the kinetic energy of a free electron doubles, its de-Broglie wavelength changes by the factor: 
 

When light is incident on a metal surface, the maximum kinetic energy of emitted electrons:
The acceptor level of a p-type semiconductor is \( 6 \) eV. The maximum wavelength of light which can create a hole would be: Given \( hc = 1242 \) eV nm.
Which figure shows the correct variation of applied potential difference (\(V\)) with photoelectric current (\(I\)) at two different intensities of light (\(I_1<I_2\)) of same wavelengths:
When a light ray incidents on the surface of a medium, the reflected ray is completely polarized. Then the angle between reflected and refracted rays is:
A microwave of wavelength 2.0 cm falls normally on a slit of width 4.0 cm. The angular spread of the central maxima of the diffraction pattern obtained on a screen 1.5 m away from the slit will be:
In YDSE, monochromatic light falls on a screen 1.80 m from two slits separated by 2.08 mm. The first and second order bright fringes are separated by 0.553 mm. The wavelength of light used is:
Young's double slit experiment is performed in a medium of refractive index \( 1.33 \). The maximum intensity is \( I_0 \). The intensity at a point on the screen where the path difference between the light coming out from slits is \( \lambda/4 \), is:
If the distance between an object and its two times magnified virtual image produced by a curved mirror is 15 cm, the focal length of the mirror must be:
In normal adjustment, for a refracting telescope, the distance between the objective and eyepiece is 30 cm. The focal length of the objective, when the angular magnification of the telescope is 2, will be:
The magnifying power of a telescope is \( 9 \). When adjusted for parallel rays, the distance between the objective and eyepiece is 20 cm. The ratio of the focal length of the objective lens to the focal length of the eyepiece is:
Power of a biconvex lens is \( P \) diopter. When it is cut into two symmetrical halves by a plane containing the principal axis, the ratio of the power of two halves is:
Electromagnetic waves travel in a medium with speed \( 1.5 \times 10^8 \) m/s. The relative permeability of the medium is \( 2.0 \). The relative permittivity will be:
A parallel plate capacitor consists of two circular plates of radius \( R = 0.1 \) m. They are separated by a short distance. If the electric field between the capacitor plates changes as: \[ \frac{dE}{dt} = 6 \times 10^{13} \frac{V}{m \cdot s} \] then the value of the displacement current is:
An alternating voltage \( V(t) = 220 \sin 100\pi t \) volt is applied to a purely resistive load of \( 50\Omega \). The time taken for the current to rise from half of the peak value to the peak value is:
In an AC circuit, an inductor, a capacitor, and a resistor are connected in series with \( X_L = R = X_C \). The impedance of this circuit is:

Find the average value of the current shown graphically from \( t = 0 \) to \( t = 2 \) s. 
 

A rectangular loop of length \( 2.5 \) m and width \( 2 \) m is placed at \( 60^\circ \) to a magnetic field of \( 4 \) T. The loop is removed from the field in \( 10 \) sec. The average emf induced in the loop during this time is:
There are two long co-axial solenoids of the same length \( l \). The inner and outer coils have radii \( r_1 \) and \( r_2 \) and the number of turns per unit length \( n_1 \) and \( n_2 \), respectively. The ratio of mutual inductance to the self-inductance of the inner coil is:
The electrostatic force \( \mathbf{F_1} \) and magnetic force \( \mathbf{F_2} \) acting on a charge \( q \) moving with velocity \( v \) can be written as:

The straight wire AB carries a current \(I\). The ends of the wire subtend angles \(\theta_1\) and \(\theta_2\) at the point \(P\) as shown in the figure. The magnetic field at the point \(P\) is: 
 


 

Five cells each of emf \(E\) and internal resistance \(r\) send the same amount of current through an external resistance \(R\) whether the cells are connected in parallel or in series. Then the ratio \(\frac{R}{r}\) is:
A wire of resistance \(160\Omega\) is melted and drawn into a wire of one-fourth of its length. The new resistance of the wire will be: