# Which electromagnetic waves travel the fastest in a vacuum?

• stickplot
In summary, the correct answer is d. All electromagnetic waves, including red, violet, and ultraviolet light, travel at the same speed in a vacuum, which is equal to the speed of light. The difference in frequency is compensated by a change in wavelength, so they all have the same velocity. The equation c = λf can be used to understand this relationship.
stickplot

## Homework Statement

Which electromagnetic waves travel the fastest in a vacuum?

a. Violet light.
b. Red light.
c. Ultraviolet light.
d. Red, violet, and ultraviolet light travel at the same speed.

ok so i thought that in a vacuum every wave traveled at the same velocity, so only the frequency could vary. I know the ultraviolet light has the highest frequency, so i was assuming d was the correct answer. But I am not so sure because d doesn't really specify they travel the same only in a vacuum but it says the travel at the same speed in general so i don't know whether it is c or d.

Do you know the relationship between wavelength and frequency of light in a vacuum? (a basic equation). Armed with that information, you won't have any doubt as to which is the correct answer.
If i was considering d, I would state an assumption along with my answer: that the phrase travel at the same speed, refers to the conditions described in the question.

are you talking about velocity= wavelength(frequency)
but I am just confused because i know all waves travel the same in a vacuum but i know frequency is higher in ultraviolet which would make the velocity greater so i don't know if its c or d

stickplot said:
are you talking about velocity= wavelength(frequency)
You are on the right track, that is the general equation. In a vacuum, it becomes $$c= \lambda f$$.
You should be familiar with the units of this expression from your https://www.physicsforums.com/showthread.php?p=2061710,#2" about the electromagnetic spectrum.
so we have;
$\lambda$ wavelength (m)
$f$ frequency (1/s)
$c$ velocity of light (m/s), c= 299,792,458 m/s

So if the frequency is higher (as you say for ultraviolet light), and you know the velocity of light,
what must change, for this equation to hold true?

Last edited by a moderator:
the wavelength needs to change, so it would be d? because the wavelength of ultraviolet light is smaller but the frequency is larger? so they would all turn out to be the speed of light right?

stickplot said:
the wavelength needs to change, so it would be d? because the wavelength of ultraviolet light is smaller but the frequency is larger? so they would all turn out to be the speed of light right?
Yes, as I stated earlier, if you understand the relationship we just discussed, you won't have any doubt what the correct answer is.

ok i understand thank you

## 1. What are electromagnetic waves?

Electromagnetic waves are a type of energy that consists of oscillating electric and magnetic fields, and they can travel through a vacuum.

## 2. What types of electromagnetic waves are there?

There are many types of electromagnetic waves, including radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays, and gamma rays.

## 3. Which electromagnetic waves travel the fastest in a vacuum?

All electromagnetic waves travel at the same speed in a vacuum, which is approximately 299,792,458 meters per second, or about 670,616,629 miles per hour.

## 4. Why do electromagnetic waves travel at the same speed in a vacuum?

This is because the speed of an electromagnetic wave is determined by the properties of the vacuum, such as the permittivity and permeability of free space, which are constants. Therefore, all electromagnetic waves have the same speed in a vacuum.

## 5. Can any medium affect the speed of electromagnetic waves?

Yes, the speed of electromagnetic waves can be affected by the properties of the medium they are traveling through. For example, the speed of light is slower in air or water compared to a vacuum, due to the molecules in the medium interacting with the electromagnetic fields.

• Introductory Physics Homework Help
Replies
4
Views
754
• Introductory Physics Homework Help
Replies
17
Views
2K
• Introductory Physics Homework Help
Replies
4
Views
209
• Introductory Physics Homework Help
Replies
5
Views
1K
• Special and General Relativity
Replies
17
Views
865
• Introductory Physics Homework Help
Replies
8
Views
2K
• Special and General Relativity
Replies
18
Views
2K
• Optics
Replies
6
Views
926
• Introductory Physics Homework Help
Replies
35
Views
2K
• Introductory Physics Homework Help
Replies
1
Views
921