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Light with an energy flux of $25 \times 10^4$ Wm$^{-2}$ falls on a perfectly reflecting surface at normal incidence. If the surface area is 15 cm$^2$, then the average force exerted on the surface is:
If c is the velocity of light in free space, the correct statements about photons among the following are: (A) The energy of a photon is E = hν. (B) The velocity of a photon is c. (C) The momentum of a photon, p = hν/c. (D) In a photon-electron collision, both total energy and total momentum are conserved. (E) Photon possesses a positive electric charge.
A uniform rope of length $L$ and mass $m_1$ hangs vertically from a rigid support. A block of mass $m_2$ is attached to the free end of the rope. A transverse pulse of wavelength $\lambda_1$ is produced at the lower end of the rope. The wavelength of the pulse when it reaches the top of the rope is $\lambda_2$. The ratio $\frac{\lambda_2}{\lambda_1}$ is:
Two waves are represented by the equations $y_1=a\sin(\omega t+kx+0.57)\text{ m}$ and $y_2=a\cos(\omega t+kx)\text{ m}$, where $x$ is in metre and $t$ in second. The phase difference between them is:
On a new scale of temperature (which is linear) and called the W scale, the freezing and boiling points of water are $39^{\circ}\text{W}$ and $239^{\circ}\text{W}$ respectively. What will be the temperature on the new scale, corresponding to a temperature of $39^{\circ}\text{C}$ on the Celsius scale?
A siren emitting a sound of frequency $800\text{ Hz}$ moves away from an observer towards a cliff at a speed of $15\text{ ms}^{-1}$. The frequency of sound that the observer hears in the echo reflected from the cliff will be: (Take, velocity of sound in air = $330\text{ ms}^{-1}$)
Planck's constant has the dimensions (unit) of
If $n_1, n_2$ and $n_3$ are the fundamental frequencies of three segments into which a string is divided, then the original fundamental frequency $n$ of the string is given by
A source of unknown frequency gives $4 \text{ beats/s}$ when sounded with a source of known frequency $250 \text{ Hz}$. The second harmonic of the source of unknown frequency gives five beats per second when sounded with a source of frequency $513 \text{ Hz}$. The unknown frequency is
The current $i$ in a coil varies with time as shown in the figure. The variation of induced emf with time would be:
The primary and secondary coils of a transformer have 50 and 1500 turns respectively. If the magnetic flux $\phi$ linked with the primary coil is given by $\phi = \phi_0 + 4t$, where $\phi$ is in Weber, $t$ is time in seconds, and $\phi_0$ is a constant, the output voltage across the secondary coil is:
A transverse wave is represented by $y=A\sin(\omega t-kx)$. For what value of the wavelength is the wave velocity equal to the maximum particle velocity?
Light travels a distance $x$ in time $t_1$ in air and $10x$ in time $t_2$ in another denser medium. What is the critical angle for this medium?
In which of the following devices, the eddy current effect is not used?
A wave in a string has an amplitude of $2 \text{ cm}$. The wave travels in the +ve direction of x-axis with a speed of $128 \text{ ms}^{-1}$ and it is noted that $5$ complete waves fit in $4 \text{ m}$ length of the string. The equation describing the wave is:
Dimensional formula for angular momentum is
The electric field in a certain region is acting radially outward and is given by E = Ar. A charge contained in a sphere of radius 'a' centered at the origin of the field will be given by:
Two periodic waves of intensities $I_1$ and $I_2$ pass through a region at the same time in the same direction. The sum of the maximum and minimum intensities is:
The fundamental frequency of a closed organ pipe of a length $20 \text{ cm}$ is equal to the second overtone of an organ pipe open at both ends. The length of the organ pipe open at both ends will be:
Which one of the following statements is true?