Question

the electro magnetic spectrum is just a name that scientists give a bunch of types of radiation when they want to talk about them as a group. use this knowledge to select all that apply.
our skin emits infrared light, which is why we can be seen in the dark by someone using night vision goggles.
radio waves emit more radiation than microwaves.
the greater the frequency, the greater the energy, the more radiation that is emitted by electromagnetic waves.
cell phones use microwaves to send and receive signals. if cell phones had been designed to run on radio waves, then cell phones would emit more radiation when in use.
our skin emits ultraviolet light, which is why we can be seen in the dark by someone using night vision goggles.
radiation is energy that travels and spreads out as it goes.

Explanation:

• Our skin emits infrared light, which is why we can be seen in the dark by someone using night vision goggles: Infrared radiation is emitted by warm objects like our skin, and night - vision goggles detect this infrared light.
• The greater the frequency, the greater the energy, the more radiation that is emitted by electromagnetic waves: According to the formula \(E = h

u\) (where \(E\) is energy, \(h\) is Planck's constant, and \(
u\) is frequency), higher - frequency electromagnetic waves have more energy.

• Radiation is energy that travels and spreads out as it goes: This is a basic definition of radiation.

• Radio waves emit more radiation than microwaves: Radio waves have lower frequencies (and thus lower energy per photon) than microwaves. So, microwaves (higher - frequency in the non - ionizing part of the EM spectrum compared to radio waves) would have more energy per photon if we consider energy of individual wave - packets (photons for quantum - mechanical view). But if we consider total power (radiation in terms of power), it depends on the source. However, generally, in terms of energy per photon (a characteristic of the wave type), radio waves (lower frequency) have less energy per photon than microwaves. So this statement is incorrect.
• Cell phones use microwaves to send and receive signals. If cell phones had been designed to run on radio waves, then cell phones would emit more radiation when in use: Radio waves have lower frequencies (lower energy per photon) than microwaves. If we assume the same power level (which is a big assumption, but in terms of energy per photon), cell - phones using radio waves would emit less energetic radiation per photon. So this statement is incorrect.
• Our skin emits ultraviolet light, which is why we can be seen in the dark by someone using night vision goggles: Our skin does not emit significant amounts of ultraviolet light (which can be harmful in excess and is mainly absorbed by the ozone layer and our skin's protective mechanisms). Night - vision goggles work on infrared, not ultraviolet. So this statement is incorrect.

Answer:

Our skin emits infrared light, which is why we can be seen in the dark by someone using night vision goggles; The greater the frequency, the greater the energy, the more radiation that is emitted by electromagnetic waves; Radiation is energy that travels and spreads out as it goes.