Ultraviolet radiation from the sun is controlled by the ozone but if it infiltrates into the atmosphere it becomes a hazard. The uv reaches our eyes and darkens the retina and blurs vision. The fovea becomes insensitive and the cells dormant. This causes gradual blindness.
Explanation:
Given that,
Two resistors of resistance 6 ohm and 3 ohm are connected in series and then in parallel.
For series combination,

For parallel combination,

When 6 ohm and 3 ohm are in series,

When 6 ohm and 3 ohm are in paralle,

So, the equivalent resistance in series combination is 9 ohms and in parallel combination it is 2 ohms.
<span>Fasteners are double or triple threaded with the idea of durability. People look for durability in a fastener and if they receive one with triple threaded or double threaded they will feel more safe and at ease knowing it has extra strength added.</span>
Assuming an ideal gas, the speed of sound depends on temperature
only. Air is almost an ideal gas.
Assuming the temperature of 25°C in a "standard atmosphere", the
density of air is 1.1644 kg/m3, and the speed of sound is 346.13 m/s.
The velocity can't be specified, since the question gives no information
regarding the direction of the sound.