An equiconvex lens has a focal length of 20 cm and its radius of curvature is 30 cm. Its refractive index is

Resistivity of a conductor depends on

The self-inductance of an inductance coil having 100 turns is 20 mH. The total flux through the coil for a current of 40 mA is :

Arrange the following materials in increasing order of their resistivities
(A) Tungsten
(B) Aluminium
(C) Gold
(D) Copper
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When light passes from air to glass, then

In a potentiometer, a cell is balanced at 240 cm. On shunting the cell with 2 \(\Omega\) resistance, the balancing comes at 120 cm. What is the internal resistance of the cell ?

Choose the correct statements from the following.
A. Like light waves, thermal radiations are also electromagnetic radiation.
B. Electromagnetic waves can travel in vacuum but mechanical waves cannot do so.
C. Gamma rays are more energetic than X-rays.
D. Microwaves are heat waves so they always produce heating.
E. Displacement current is a fictious current and has nothing in common with conduction current.
Choose the correct answer from the options given below:

Read the passage carefully and answer the questions
Optically active polyhydroxy aldehydes or ketones or molecules which provide such units on hydrolysis are called carbohydrates. They can be broadly classified as monosaccharides, disaccharides and polysaccharides depending on their behavior towards hydrolysis. They are also classified as reducing or non-reducing sugars. Another class of biomolecules is proteins which are polymers of twenty different amino acids linked by peptide bonds. Amino acids can be classified as acidic, basic or neutral depending on the relative number of amino and carboxyl groups in their molecule. The essential amino acids cannot be synthesized by our body and hence must be provided through diet. Nucleic acids are the polymers of nucleotides which in turn consist of a base, pentose sugar and phosphate. There are two types of nucleic acids namely, DNA and RNA which differ in the composition of sugar and a base
The sugar moiety in DNA and RNA molecules, respectively, ar

Appearance of resistant organisms in a time scale of months or years, by the excessive use of antibiotics is an example of which of the following?

Two point charges \( 2 \, \mu\text{C} \) and \( 3 \, \mu\text{C} \) are placed at a distance of 5 cm from each other. The magnitude of the electrostatic force between them is:

Match List-I with List-II

List-I (Physical quantity)	List-II (Unit)
(A) Electric flux	(I) V m−1
(B) Polarisation	(II) kg m−1⁢ s−2
(C) Electric field	(III) V m
(D) Energy density	(IV) C m−2

Choose the correct answer from the options given below:

A wire of resistance \( 5\Omega \) is drawn out so that its length is increased by thrice its original length. The new resistance would be :

Identify the diagnostic test used to detect the sex of the foetus from the following: