Question

We spend our lives in visible light without risks to our health. Yet exposure to UV waves in sunlight can cause skin cancer. What is the BEST explanation for this?
A) UV waves are longer and carry more energy.
B) UV waves are higher frequency and carry more energy.
C) UV waves have a lower frequency and carry more energy.
D) UV waves travel faster than visible light and have more energy.

Answer 1

UV waves are higher frequency and carry more energy causing exposure to UV waves in sunlight to skin cancer. This is a type of electromagnetic radiation similar to the waves of the radio, infrared, x-rays and gamma. All of which comes from the sun however cannot be seen by a human eye. People use these rays for tanning however if it is overdone, it may cause skin problems.

Answer 2

The correct answer is
B) UV waves are higher frequency and carry more energy. 

In fact, UV waves have higher frequency than visible light. For comparison, visible light has frequency in the range 430-770 THz ($10^{12} Hz$), while ultraviolets (UV) have frequency higher than these values (at the order of 1 PHz, $1\cdot 10^{15}Hz$).

The energy of electromagnetic radiation is proportional to its frequency, according to the equation
$E=hf$
where h is the Planck constant and f is the frequency. We see that the higher the frequency, the greater the energy, so UV waves carry more energy than visible light.