Tove feels the warmth of sunlight on her face. That light crossed the space between the Sun and Earth, and that space holds no air at all.
Every mechanical wave you met needed a medium. This lesson shows that electromagnetic waves do not.
Sound could never make the Sun-to-Earth trip. In the waves topic, a ringing bell fell silent as the air was pumped out of a bell jar: a mechanical wave needs a medium.
The space between the Sun and Earth is completely empty space, a vacuum.
A vacuum holds no air, no water, no material of any kind.
Yet sunlight crosses that vacuum and reaches Tove's face.
So light needs no medium.
They can also travel through materials, like air, water, and glass. The point is that they never need one.
Moonlight crosses the empty space between the Moon and Earth. What carries the wave across?
The space between the Moon and Earth is a vacuum: completely empty space.
Moonlight is an electromagnetic wave, and electromagnetic waves need no medium.
Nothing carries it. The wave crosses the vacuum on its own.
A space probe near Jupiter sends a radio signal back to Earth, across hundreds of millions of kilometers of empty space. What does the signal need in order to cross?
A radio signal is an electromagnetic wave.
The space along the way is a vacuum, and an electromagnetic wave needs no medium.
It needs nothing along the way. The signal crosses the vacuum on its own.
The air is pumped out of a sealed glass chamber until almost nothing is left inside. A flashlight beam still crosses the chamber and lights the far side. What does this show?
Selby says: 'Every wave, including light, needs some material to travel through.' Is Selby correct?
Rurik says: 'Light can cross completely empty space, with no material to carry it.' Is Rurik correct?
Which statement about electromagnetic waves is true?
An astronaut on a spacewalk drifts outside the station, where there is no air. She still sees the station's lights. Which statement explains how the light reached her?
Which of the following is a vacuum?