To obtain the powerful parallel beams of light from a vehicle's headlight, one must use
front surface silvered plane mirror
back surface silvered plane mirror
concave mirror
convex mirror
C.
concave mirror
Because a parabola allows the light rays to be focused as a single beam and gives more power to the light, so it is more efficient for seeing and being seen. If the mirror were spherical, the light would be scattered much more, which wasted energy and reduces efficiency
Which one among the following denotes the smallest temperature?
1° on the Celsius scale
1° on the Kelvin scale
1° on the Fahrenheit scale
1° on the Reaumur scale.
A fan produces a feeling of comfort during hot weather, because
our body radiates more heat in air
fan supplies cool air.
conductivity of air increases
our perspiration evaporates rapidly
Which one among the following methods is not effective in removing arsenic from contaminated groundwater?
Boiling
Reverse osmosis
Ion exchange
Coagulation-adsorption
