Solution (a)

The loudness of sound depends on its amplitude and the frequency determines the pitch of a sound.

Hence statement 1 correct

The range of audible frequencies for a human ear is roughly from 20 to 20,000 vibrations per second (20 to 20,000 Hz). 

Hence statement 2 incorrect

Solution (d)

A rainbow is a meteorological phenomenon that is caused by Total Internal Reflection, Refraction and Dispersion of light in water droplets resulting in a spectrum of light appearing in the sky.

Solution (c)

When all the parallel rays reflected from a plane surface are not parallel, the reflection is known as diffused or irregular reflection. 

Hence statement 1 is correct

The diffused reflection is not due to the failure of the laws of reflection. It is caused by the irregularities in the reflecting sur face

Hence statement 2 incorrect

The diffused reflection is caused by the irregularities in the reflecting surface, like that of a cardboard.

Hence statement 3 is correct

Solution (c)

The image formed by a concave mirror can be smaller or larger in size than the object. 

Concave mirrors are commonly used in torches, search-lights and vehicles headlights to get powerful parallel beams of light.

Hence statement 1 is incorrect

Convex mirrors can form images of objects spread over a large area. So, these help the drivers to see the traffic behind them.

Hence statement 2 is correct

The image formed by a concave mirror may be real or virtual.

Hence statement 3 is incorrect

Solution (b)

The Nobel Prize in Physics is awarded by The Royal Swedish Academy of Sciences, Stockholm, Sweden.

Hence statement 1 is correct

The candidates eligible for the Physics Prize are those nominated by qualified persons who have received an invitation from the Nobel Committee to submit names for consideration. No one can nominate himself or herself.

Hence statement 2 is incorrect

The statutes of the Nobel Foundation restrict disclosure of information about the nominations, whether publicly or privately, for 50 years. 

Hence statement 3 is correct

Solution (d)

Total Internal Reflection:

If light is propagating from denser medium towards the rarer medium and angle of incidence is more than critical angle, then the light incident on the boundary is reflected back in the denser medium, obeying the laws of reflection. This phenomenon is called total internal reflection as total light energy is reflected, no part is absorbed or transmitted.

For total internal reflection,

1) Light must be propagating from denser to rarer medium

2) Angle of incidence must exceed the critical angle

Solution (d)

Similar to batteries and all other electrochemical cells, fuel cells have two electrodes, and an electrolyte sandwiched in between. Fuel cells are distinguished by the type of electrolyte they use. The more common fuel cells on the market are:

PEM “Polymer Exchange Membrane” also known as “Polymer Electrolyte Membrane” Fuel Cell (PEMFC)

“Solid Oxide” Fuel cell (SOFC),

“Molten Carbonate” Fuel cell (MCFC),

Solution (c)

Friction force is an example of a contact force. Rest of the three forces acts from a distance and don’t require body to body contact.

Contact Forces

Action-at-a-Distance Forces

Frictional Force

Gravitational Force

Tension Force

Electrical Force

Normal Force

Magnetic Force

Air Resistance Force

Applied Force

Spring Force

Solution (b)

The object will be in inertia of motion. As it was moving with train, it had a component of velocity in the direction of motion. If it is released, that component will still be there and it will fall in the direction of motion of the train.

Solution (b)

Steam burns are more severe as steam contains more heat in the form of latent heat.