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The filament of a light bulb has a surface area 64 mm². The filament can be considered as a black body at temperature 2500 K emitting radiation like a point source when viewed from far. At night the light bulb is observed from a distance of 100 m. Assume the pupil of the eyes of the observer to be circular with radius 3 mm. Then

(Take Stefan-Boltzmann constant = 5.67 × 10−8 Wm−2K−4, Wien’s displacement constant = 2.90 × 10−3m-K, Planck’s constant = 6.63 ×... View Article

A particle of mass m moves in circular orbits with potential energy V( ) = , where F is a positive constant and r is its distance from the origin. Its energies are calculated using the Bohr model. If the radius of the particle’s orbit is denoted by R and its speed and energy are denoted by v and E, respectively, then for the n^th orbit (here h is the Planck’s constant)

Answer: b, c P.E., V(r) = Fr Therefore, Force = -dV/dr = – F F = mv2 / R ….... View Article

An open-ended U-tube of uniform cross-sectional area contains water (density 10³kg m⁻³). Initially, the water level stands at 0.29 m from the bottom in each arm. Kerosene oil (a water-immiscible liquid) of density 800 kg m⁻³ is added to the left arm until its length is 0.1 m, as shown in the schematic figure below. The ratio h₂ / h₂ of the heights of the liquid in the two arms is

a) 15 / 14 b) 35 / 33 c) 7 / 6 d) 5 / 4 Answer: b ∵ Pressure... View Article

A parallel beam of light strikes a piece of transparent glass having cross section as shown in the figure below. Correct shape of the emergent wavefront will be (figures are schematic and not drawn to scale)

Answer: a Concept: based on Huygens’ principle. Theory of wavefront → wave moves such that direction of propagation is perpendicular... View Article

A circular coil of radius R and N turns has negligible resistance. As shown in the schematic figure, its two ends are connected to two wires and it is hanging by those wires with its plane being vertical. The wires are connected to a capacitor with charge Q through a switch. The coil is in a horizontal uniform magnetic field B_o parallel to the plane of the coil. When the switch is closed, the capacitor gets discharged through the coil in a very short time. By the time the capacitor is discharged fully, magnitude of the angular momentum gained by the coil will be (assume that the discharge time is so short that the coil has hardly rotated during this time)

a) /2 2 b) 2 c) 2 2 d) 4 2 Answer: b After closing switch, within a fraction of... View Article

A small roller of diameter 20 cm has an axle of diameter 10 cm (see figure below on the left). It is on a horizontal floor and a meter scale is positioned horizontally on its axle with one edge of the scale on top of the axle (see figure on the right). The scale is now pushed slowly on the axle so that it moves without slipping on the axle, and the roller starts rolling without slipping. After the roller has moved 50 cm, the position of the scale will look like (figures are schematic and not drawn to scale)

Answer: b ∵ In this case pure rolling without slipping, Let radius of roller is R and radius of axle... View Article

A light disc made of aluminium (a nonmagnetic material) is kept horizontally and is free to rotate about its axis as shown in the figure. A strong magnet is held vertically at a point above the disc away from its axis. On revolving the magnet about the axis of the disc, the disc will (the figure is schematic and not drawn to scale)

a) rotate in the direction opposite to the direction of magnet’s motion b) rotate in the same direction as the... View Article

A football of radius R is kept on a hole of radius r( < ) made on a plank kept horizontally. One end of the plank is now lifted so that it gets tilted making an angle θ from the horizontal as shown in the figure below. The maximum value of θ so that the football does not start rolling down the plank satisfies (the figure is schematic and not drawn to scale)

a) sin θ = r / R b) tan θ = r / R c) sin θ = r /... View Article

On the basis of information given in Column – I and Column – II match the reactant with the products.

Which of the following is correct? a) Q – I, IV, VI; R – II, III, V b) Q –... View Article

Match the reactant in column – I with the possible intermediates and products of Column – II

Which of the following is correct? a) P – II, III; S – II, III b) P – II, IV;... View Article

Match the column and choose the correct option

Answer the following by appropriately matching the lists based on the information given in the paragraph. Consider Bohr’s model of... View Article

Match the column and state which of the given options is correct

Answer the following by appropriately matching the lists based on the information given in the paragraph. Consider Bohr’s model of... View Article

Number of N-Mn-Cl bonds [N-Mn bonds is cis to Mn-Cl bond] in cis [Mn(en)₂Cl₂] are

Answer: 6 This is the Cis form of [Mn(en)2Cl2] Therefore, No. of N–Mn–Cl bonds = 6

In following reaction the value of K is 5 × 10^-4 S^-1.

Initial pressure was 1 atm, while the final pressure was 1.45 atm at time y × 103 sec calculate ‘y’.... View Article

Number of hydroxyl group in compound ‘Y’ is:

Answer: The number of hydroxyl group in compound ‘Y’ = 6 – OH groups As you can see there are... View Article

Mole fraction of urea in 900 gram water is 0.05. Density of Solution is 1.2 g/cm³. Find molarity of Solution.

Answer: 2.99 Number of moles of H2O = 900/18 = 50 n1/(n1+50) = 0.05 (n1 is No. of moles of... View Article

Who Did British Defeat in Battle of Plassey?

British defeated Nawab of Bengal, Siraj-ud-Daulah in the Battle of Plassey. To read more about the Battle of Plassey, check... View Article

1 mole of Rhombic sulphur is treated with conc. HNO₃. Find the mass of H₂O formed.

Answer: 288 Solution: S8 + HNO3 → H2SO4 + NO2 + H2O Balancing the equation, S8 + x HNO3 → 8 H2SO4... View Article

Calculate the total number of cyclic ether (including stereo) having formula C₄H₈O.

Answer: 10 Total 10

For He⁺ the electron is in orbit with energy equal to 3.4eV. The azimuthal quantum number for that orbit is 2 and magnetic quantum number is 0. Then which of the following is/are correct.

a) The subshell is 4d. b) The number of angular nodes in it is 2. c) The numbers of radial... View Article

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