U = I × R = 20A × 12 Ohm =240V
The correct answer of this question is : A) Radio waves have longer wavelengths, lower frequency, and lower energy than ultraviolet waves and x-rays.
EXPLANATION :
Before going to answer this question, first we have to know the electromagnetic spectrum.
Electromagnetic spectrum is the arrangement of electromagnetic waves in the ascending order of frequency or descending order of wavelength.
When the waves are arranged in the ascending order of their frequency, then perfect order is given below as such -
Radio wave < Micro wave < Infrared wave < Visible light < U.V ray< X-ray < Gamma ray .
Hence, we see that radio wave has the least frequency, and gamma ray has the most frequency.
We know that wavelength and frequency are inversely are inversely proportional to each other. Hence, radio wave has more wavelength and less frequency.
The wave having more frequency is more energetic. Hence, gamma is more energetic and radio wave is less energetic .
Answer: C. good reflector of heat
Explanation:
In space, sunlight transfers heat by radiation to objects and bodies and this includes satellites and astronauts. In addition, although the peak of the sun's emission is in the visible region of the electromagnetic spectrum, a part is also emitted in infrared (transferring thermal energy or heat) and ultraviolet (especially in the upper part of the Earth's atmosphere).
That is why in space missions, objects and many satellites are covered by thin layers or sheets that reflect this thermal energy and thus avoid damaging the equipment due to high temperatures.
In this sense, among the reflective materials used are aluminum, silver, copper and gold; the latter being the most used because it does not corrode or oxidize (unlike silver and copper) and is more malleable than aluminum.
On the other hand, <u>astronauts are also vulnerable to the effects of infrared radiation, especially their eyes</u>, since the human eye has no receptors in the infrared spectrum. <u>That is why the astronaut's helmet visor is covered with a thin layer of gold to avoid the dangerous effects of solar radiation.</u>
The answer is observation
Since the two trains are passing in opposite
directions, so this means that their relative velocities will be the sum of the
two trains that is:
<span>
relative velocity = (13 + 28) = 41m/s</span>
<span>
a. The passengers aboard on train B will see that train A is
moving at 41m/sec due east</span>
<span>b. The passengers aboard on train A will see that
train B is moving at 41m/sec due west</span>
