I need to check my answers!!

Question

Which of these is not in the family
a. sound
b. light
c. infrared radiation (answer)
d. radio waves

When an electric charge is shaken to and fro in quick succession, the vibrating charge emits
a. infrasonic sound
b. Ultrasonic sound
c. an electromagnetic wave (answer)
d. gamma radiation

If you dip your finger repeatedly onto the surface of still water, you produce waves. The more frequently you dip your finger, the
a. lower the wave frequency and the longer the wavelength
b. higher the wave frequency and the shorter the wavelength (answer)
c. both of the above
d. neither

Low-pitched sounds have
a. low frequencies
b. long periods
c. both (answer)
d. none

I was so confused by this question!! Any advice??

Suppose at a concert a singer’s voice is a radio broadcast all the wave around the world before reaching the radio you hold to your ear. This takes 1/8 seconds. If you’re close, you her her voice in the air before you hear it from the radio. But, if you are far away, both singnals will reach you at the same time. How many meters distant must you be for this to occur!!

Would it be 1 meter or 8 meters?? I think it’s 8!