Monochromatic radiation emitted when electron on hydrogen atom jumps from first excited to the ground state irradiates a photosensitive material. The stopping potential is measured to be \(3.57~\text{V}\). The threshold frequency of the material is:
1. \(4\times10^{15}~\text{Hz}\)
2. \(5\times10^{15}~\text{Hz}\)
3. \(1.6\times10^{15}~\text{Hz}\)
4. \(2.5\times10^{15}~\text{Hz}\)
\(\mathrm{ABC}\) is an equilateral triangle with \(O\) as its centre. \(F_1,\) \(F_2,\) and \(F_3\) represent three forces acting along the sides \({AB},\) \({BC}\) and \({AC}\) respectively. If the total torque about \(O\) is zero, then the magnitude of \(F_3\) is:
| 1. | \(F_1+F_2\) | 2. | \(F_1-F_2\) |
| 3. | \(\dfrac{F_1+F_2}{2}\) | 4. | \(2F_1+F_2\) |
The figure shows a logic circuit with two inputs \(A\) and \(B\) and the output \(C\). The voltage waveforms across \(A\), \(B\), and \(C\) are as given. The logic circuit gate is:
1. \(\text{OR}\) gate
2. \(\text{NOR}\) gate
3. \(\text{AND}\) gate
4. \(\text{NAND}\) gate
What is the flux through a cube of side \(a,\) if a point charge of \(q\) is placed at one of its corners?
| 1. | \(\dfrac{2q}{\varepsilon_0}\) | 2. | \(\dfrac{q}{8\varepsilon_0}\) |
| 3. | \(\dfrac{q}{\varepsilon_0}\) | 4. | \(\dfrac{q}{2\varepsilon_0}\) |
An \(\alpha\text-\)particle moves in a circular path of radius \(0.83~\text{cm}\) in the presence of a magnetic field of \(0.25~\text{Wb/m}^2.\) The de-Broglie wavelength associated with the particle will be:
1. \(1~\mathring{A}\)
2. \(0.1~\mathring{A}\)
3. \(10~\mathring{A}\)
4. \(0.01~\mathring{A}\)
1. \(2~\text{m}^{-1}\)
2. \(0.5~\text{m}^{-1}\)
3. \(6~\text{m}^{-1}\)
4. \(3~\text{m}^{-1}\)
The motion of a particle along a straight line is described by the equation \(x = 8+12t-t^3\) where \(x \) is in meter and \(t\) in seconds. The retardation of the particle, when its velocity becomes zero, is:
| 1. | \(24\) ms-2 | 2. | zero |
| 3. | \(6\) ms-2 | 4. | \(12\) ms-2 |
The magnifying power of a telescope is \(9\). When it is adjusted for parallel rays the distance between the objective and eyepiece is \(20~\text{cm}\). The focal length of the lenses is:
| 1. | \(10~\text{cm}, ~10~\text{cm}\) | 2. | \(15~\text{cm}, ~5~\text{cm}\) |
| 3. | \(18~\text{cm}, ~2~\text{cm}\) | 4. | \(11~\text{cm}, ~9~\text{cm}\) |
Two sources of sound placed close to each other, are emitting progressive waves given by,
\(y_1=4\sin 600\pi t\) and \(y_2=5\sin 608\pi t\).
An observer located near these two sources of sound will hear:
| 1. | \(4\) beats per second with intensity ratio \(25:16\) between waxing and waning |
| 2. | \(8\) beats per second with intensity ratio \(25:16\) between waxing and waning |
| 3. | \(8\) beats per second with intensity ratio \(81:1\) between waxing and waning |
| 4. | \(4\) beats per second with intensity ratio \(81:1\) between waxing and waning |
A ring is made of a wire having a resistance of \(R_0=12~\Omega.\). Find points \(\mathrm{A}\) and \(\mathrm{B}\), as shown in the figure, at which a current-carrying conductor should be connected so that the resistance \(R\) of the subcircuit between these points equals \(\frac{8}{3}~\Omega\)
| 1. | \(\dfrac{l_1}{l_2} = \dfrac{5}{8}\) | 2. | \(\dfrac{l_1}{l_2} = \dfrac{1}{3}\) |
| 3. | \(\dfrac{l_1}{l_2} = \dfrac{3}{8}\) | 4. | \(\dfrac{l_1}{l_2} = \dfrac{1}{2}\) |
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