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Sound travels in the form of _____.

An auto travels the first half of the total time with a uniform speed u and the other half with a uniform speed v. Find its average speed.

What kind of effects can we see when an electric current is produced while flowing through a conducting solution?
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In the figure shown, wave $A$ is reflected from surface $PQ$ while wave $B$ is reflected from the surface $RS$. If $\mu$ is the refractive index of the glass slab and $t$ is its thickness, the path difference between the reflected waves of $A$ and $B$ is, (Assume that both waves are incident on surface $PQ$ at the same instant)

At what angle of incidence will the light reflected from the glass $(\mu =1.5)$ be completely polarised?

Question 9

The danger signals installed at the top of tall buildings are red in colour. These can be easily seen from a distance because among all other colours, the red light:



(a) is scattered the most by smoke or fog

(b) is scattered the least by smoke or fog

(c) is absorbed the most by smoke or fog

(d) moves fastest in air

A siphon in use is demonstrated in the following figure. The density of the liquid flowing in siphon is 1.5 gm/cc. The pressure difference between the point P and S will be

In order to get a diminished and virtual image, the object can be placed anywhere in front of :

How does sun produces light in vaccum?

A sound wave has a time period of 0.5s. What is the frequency of the wave?

Select the correct option:

I) A magnetic needle responds to the Earth’s magnetic field.

II) A magnetic needle gets deflected when a magnet is brought near it.

III) A magnetic needle is made up of a non-magnetic material.

Radiation from the Sun reaching Earth (just outside the atmosphere) has an intensity of $1.4{\text{kW/m}}^2$. If $F_R$ is the force on Earth due to radiation pressure and $F_g$ is the force due to the Suns gravitational attraction, then select the correct option (Assuming that Earth (and its atmosphere) behaves like a flat disk perpendicular to the Suns rays and that all the incident energy is absorbed)

$[\text{Take}{\text{R}}_{earth}=6400\text{km},M_{earth}=5.98\times {10}^{24}\text{kg},M_{sun}=2\times {10}^{30}\text{kg},\text{Distance between the centres of Sun and Earth}=1.5\times {10}^8\text{km}]$

A space ship travells 36000 km/hr. Express its speed in km/s.

In a series combination of electrical appliances, connected to a constant voltage power supply, if we add one more appliance with resistance R in series, then the total electrical power consumed in the circuit will__.

The emf of a storage battery is $90V$ before charging and $100V$ after charging. When charging began the current was $10A$. What is the current at the end of charging if the internal resistance of the storage battery during the whole process of charging may be taken as constant and equal to 2 $\Omega$?

In order to hear distinct echoes, the distance of the obstacle from the source of sound should be at least:

Which of the following diagrams correctly represents the magnetic field due to a bar magnet?

Statement 1: Force acting on a body increases its kinetic energy from 200 J to 400 J and this force does a positive work on the body.

Statement 2: A force does a positive work on an object when the displacement is in the direction of force itself.

How woolen clothes have a layer of air between two layers of cloth

We can increase the strength of an electromagnet by increasing the number of turns of wire on the coil and but is there any other method with the help of which we can increase the strength of an electromagnet?

A cylindrical metallic wire is stretched to increase its length by 5%. Calculate the percentage change in resistance.

Give reasons.

(a) The sun, the earth and the moon must be in a straight line for an eclipse to occur.

(b) The penumbra is faint.

(c) An aeroplane or a bird does not cast a shadow upon the earth.

(d) We get an upside down image in a pinhole camera.