Question

1. Electromagnetic waves occur because

   		A changing magnetic field induces an electric field, but a changing electric field does nothing
   		A changing electric field induces a magnetic field, but a changing magnetic field does nothing
   		A changing magnetic field induces an electric field, and a changing electric field induces a magnetic field
   		There are no constant electric and magnetic fields

2. Comparing microwave and ultraviolet (UV):

		Microwave has longer wavelength and higher photon energy
		Microwave has longer wavelength and lower photon energy
		UV has longer wavelength and higher photon energy
		UV has longer wavelength and lower photon energy

3. Typical analog cell phones use a frequency of 850 MHz while digital cell phones use 1950 MHz. Compared to the analog signal the digital signal has

		Longer wavelength and lower photon energy
		Longer wavelength and higher photon energy
		Shorter wavelength and lower photon energy
		Shorter wavelength and higher photon energy

Answer 1

1) electromagnetic waves occur because electric field and magnetic field are self-perpetuating, that is changes in magnetic field induces electric field and changes in electric field induces magnetic field option 3

2) E = hc/ so less the wavelength more the energy Uv wavelength is 10^-8,microwave  wavelength is 10^-1 so option b microwave has higher wavelength and lower photon energy

3) =c/ so less frequency more wavelength and E= h so digital signal has shorter wavelength higher photon energy