Ultraviolet (UV) rays from the Sun play a dual role in our environment. On the positive side, UV radiation facilitates the production of vitamin D in our skin, which is essential for maintaining bone health and various bodily functions. On the downside, overexposure to UV rays can be harmful. It can lead to sunburn and prolonged exposure increases the risk of skin cancer. UV radiation can also cause cataracts and other eye damage. Therefore, while limited sun exposure is beneficial, precautions like using sunscreen and wearing protective clothing are vital to mitigate the harmful effects of UV rays.

X-rays are a form of electromagnetic radiation with shorter wavelengths than visible light, which allows them to penetrate through soft tissues. In medical imaging, a machine produces a controlled amount of X-rays. When directed towards a patient, these X-rays can pass through softer tissues like muscles but are absorbed by denser ones like bones. Detectors on the other side capture the unabsorbed X-rays, creating a contrast image which reveals the internal structure. The varying degrees of absorption of these rays by different tissues allow for detailed imagery, aiding in diagnosis and treatment planning.

The blue colour of the sky is a result of Rayleigh scattering. Earth's atmosphere comprises small particles that scatter shorter wavelengths of light, like blue and violet, more than longer wavelengths like red and yellow. However, our eyes are more sensitive to blue light, making the sky predominantly appear blue during the day. On the other hand, during sunrise and sunset, the sun's position results in its light traversing a longer path through the atmosphere. This increased distance causes shorter wavelengths to scatter out and get dispersed, allowing the longer wavelengths (reds and oranges) to dominate, resulting in a red-hued sky.

The greenhouse effect is closely tied with infrared radiation. The Earth receives energy from the Sun in the form of visible light and other types of electromagnetic radiation. After absorbing this energy, the Earth emits it back into space as infrared radiation. Greenhouse gases in our atmosphere, like carbon dioxide and methane, trap some of this outgoing infrared radiation. These gases absorb the infrared radiation and re-radiate it in all directions, including back towards the Earth's surface. This trapped radiation warms the planet and results in the greenhouse effect. It's essential for sustaining life as it keeps the Earth warm, but excessive greenhouse gases amplify this effect, leading to global warming.

The electromagnetic spectrum encompasses a vast range of wavelengths and frequencies, with radio waves and gamma rays on opposite ends. Radio waves have longer wavelengths and lower frequencies, while gamma rays have shorter wavelengths and higher frequencies. The propagation of radio waves allows them to bend around obstacles and refract through the atmosphere, giving them a longer range. Gamma rays, due to their short wavelength and high energy, are more likely to interact with matter and get absorbed, limiting their range. Additionally, their high energy makes them more ionising, which means they can easily be blocked by even thin sheets of materials, whereas radio waves can penetrate through various obstacles.