Curved mirror that reflects light from its inner surface, the curve being inward. It may be either circular or parabolic in section. A concave mirror converges parallel light rays inward to the point of principal focus. The image formed by a concave mirror is real (reduced and inverted) if the object is not too close to the mirror. A real image is formed at the point of convergence. If the object is close to the mirror then the image formed will be virtual, enlarged, and upright, as the rays of light cannot converge to a point. Only a parabolic concave mirror has a true, single-point principal focus for parallel rays. For this reason, parabolic mirrors are used as reflectors to focus light in telescopes, or to focus microwaves in satellite communication systems.

Correct Option: A

Curved mirror that reflects light from its inner surface, the curve being inward. It may be either circular or parabolic in section. A concave mirror converges parallel light rays inward to the point of principal focus. The image formed by a concave mirror is real (reduced and inverted) if the object is not too close to the mirror. A real image is formed at the point of convergence. If the object is close to the mirror then the image formed will be virtual, enlarged, and upright, as the rays of light cannot converge to a point. Only a parabolic concave mirror has a true, single-point principal focus for parallel rays. For this reason, parabolic mirrors are used as reflectors to focus light in telescopes, or to focus microwaves in satellite communication systems.

A psychrometer consists of two thermometers, one which is dry and one which is kept moist with distilled water on a sock or wick. The two thermometers are thus called the dry-bulb and the wet-bulb. Relative humidity is computed from the ambient temperature as shown by the dry-bulb thermometer and the difference in temperatures as shown by the wet-bulb and dry-bulb thermometers. The sling psychrometer, where the thermometers are attached to a handle or length of rope and spun around in the air for a few minutes, is sometimes used for field measurements, but is being replaced by more convenient electronic sensors.

Correct Option: C

A psychrometer consists of two thermometers, one which is dry and one which is kept moist with distilled water on a sock or wick. The two thermometers are thus called the dry-bulb and the wet-bulb. Relative humidity is computed from the ambient temperature as shown by the dry-bulb thermometer and the difference in temperatures as shown by the wet-bulb and dry-bulb thermometers. The sling psychrometer, where the thermometers are attached to a handle or length of rope and spun around in the air for a few minutes, is sometimes used for field measurements, but is being replaced by more convenient electronic sensors.

Gravity is pulling the man down while friction with the air slows him down. With the parachute out it adds more friction slowing him down because air resistance works against the very large surface area of the parachute. A free falling skydiver that has not yet opened his parachute can make his downward speed vary between about 110 mph and 225 mphusing air resistance. A spread eagled position presents the maximum area, and we fall the slowest.

Correct Option: C

Gravity is pulling the man down while friction with the air slows him down. With the parachute out it adds more friction slowing him down because air resistance works against the very large surface area of the parachute. A free falling skydiver that has not yet opened his parachute can make his downward speed vary between about 110 mph and 225 mphusing air resistance. A spread eagled position presents the maximum area, and we fall the slowest.

The temperature may fall below 00 C during cold frosty nights which converts the water inside the pipes into ice, resulting in an increase in volume. This exerts great force on the pipes and as a result, they burst.

Correct Option: B

The temperature may fall below 00 C during cold frosty nights which converts the water inside the pipes into ice, resulting in an increase in volume. This exerts great force on the pipes and as a result, they burst.

It is tidal locking that causes the synchronous rotation which causes the Moon to present “just one side” to the Earth all the time. The Moon rotates (spins) but very slowly, making one turn on its axis in the same time it takes to revolve (orbit) around the Earth. So it maintains a “constant face” in our direction. We actually see slightly more than half of its surface as it turns. Tidal locking (or captured rotation) occurs when the gravitational gradient makes one side of an astronomical body always face another, an effect known as synchronous rotation. For example, the same side of the Earth’s Moon always faces the Earth. A tidally locked body takes just as long to rotate around its own axis as it does to revolve around its partner. This causes one hemisphere constantly to face the partner body.

Correct Option: C

It is tidal locking that causes the synchronous rotation which causes the Moon to present “just one side” to the Earth all the time. The Moon rotates (spins) but very slowly, making one turn on its axis in the same time it takes to revolve (orbit) around the Earth. So it maintains a “constant face” in our direction. We actually see slightly more than half of its surface as it turns. Tidal locking (or captured rotation) occurs when the gravitational gradient makes one side of an astronomical body always face another, an effect known as synchronous rotation. For example, the same side of the Earth’s Moon always faces the Earth. A tidally locked body takes just as long to rotate around its own axis as it does to revolve around its partner. This causes one hemisphere constantly to face the partner body.