The focal length of a convex lens in air and in a liquid medium are 20 cm and 80 cm, respectively. If the absolute refractive index of lens is 1.5, then the refractive index of liquid is :

The electron in a hydrogen atom emits wavelengths \( \lambda_1, \lambda_2, \lambda_3, \lambda_4 \) in the following transitions (A), (B), (C), and (D), respectively. Arrange the transitions in the increasing order of emitted wavelengths:
(A) n = 3 to n = 2
(B) n = 4 to n = 3
(C) n = 4 to n = 2
(D) n = 2 to n = 1
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A closed surface in vacuum encloses charges \( - q \) and \( + 3q \). Another charge \( - 2q \) lies out side the surface. The total electric flux over the surface is :

A moving coil galvanometer has 100 equal divisions. Its current sensitivity is 20 divisions per mA and voltage sensitivity is 4 divisions per mV. To convert it into a voltmeter in which each division reads 1 V, the resistance needed to be connected in series with the coil will be :

Identify the correct statements in the following:
(A) Optical fibres consist of a core and cladding
(B) Optical fibres are fabricated such that light reflected at one side of the inner surface strikes the other at an angle smaller than the critical angle.
(C) Optical fibres make use of the phenomenon of total internal reflection.
(D) Optical fibres can be used as an optical pipe
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Which of the following statements are correct?
(A) The resistance of a conductor and its resistivity both depend on temperature.
(B) For a conductor of 1 m length and of \( 1 \text{ m}^2 \) cross-sectional area, the resistance is equal to its resistivity
(C) Resistance and resistivity both depend on cross-sectional area
(D) The resistivity of two wires made of same material but of different dimensions is the same.
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Electric field intensity at a point varies as \( \frac{1}{r^3} \) due to:

RNA interference involves silencing of a specific mRNA due to complementarity of

Maximum number of male gametes produced from one pollen mother cell (microspore mother cell) will be:

A very long straight wire carries a current (I) directed along positive Y-axis. A point charge +Q moves with velocity (v) along X -axis. The direction of force on the charge at point (5,0,0) m is

Answer the question on the basis of passage given below:
Second period elements of p-Block differs from the rest of their group members due to their small atomic size, high electronegativity, high ionization enthalpy and absence of d-orbitals. The elements from the second period like C, N, O have unique property of forming \(p \pi-p \pi\) multiple bonds whereas other heavier elements of p-block form \(d \pi-p \pi\) multiple bonds. This changes the properties of second period elements to great extent. Also the single bond strength of the p-block elements with their own atoms gets affected by their atomic size and presence of lone pairs.
Inert pair effect also affects the properties of the p-Block elements especially for those elements which are present from 4th period onward and this happens due to poor screening effect of inner (n-1)d subshell electrons.
Catenation tendency of Nitrogen is weaker than Phosphorus, because

An electron in the ground state goes to the first excited state in the hydrogen atom. Arrange the following energies in decreasing order:
(A) Total energy in ground state
(B) Kinetic energy in ground state
(C) Potential energy in ground state
(D) Total energy in first excited state
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A charged particle is moving in a cyclotron. What is the effect on time for one revolution of this charged particle, when its radius of the orbit is doubled?