"Investigating the Speed of Reflections in Mirrors"

[wilha]

We are able to see things around us due to the reflection of light, but while standing in front of a mirror we see our own reflection. And the moment we move our reflection moves as well

My question: Since light reflects off us, then into the mirror, and back to our eyes, does it mean that our reflection is technically slower than our movements and the difference is so minute that it goes unnoticed to our eyes ?

 

[Antiphon]

Yes.

 

[wilha]

Thanks, i asked my teacher the same question, he didn't have a clear answer.

 

[Born2bwire]

The speed of light though is almost 30,000,000 m/s. So while the reflection is slower, the time lag is only noticeable over very large distances or with very sensitive methods of measuring. For example, the light emitted by the Sun takes around 8 minutes to reach the Earth in an often quoted example.

 

[onlyyou200548]

i agree with Born2bwire. but the speed of light is actually almosl 300,000,000 m/s

 

[Born2bwire]

i agree with Born2bwire. but the speed of light is actually almosl 300,000,000 m/s

Dammit, I should have stuck with scientific notation.

 

[sophiecentaur]

I assume we're talking non-relativistic speeds here.
The word "slower" could be confusing and the issue should be cleared up. There will be a time lag of everything you observe of about 3ns for every metre away the object is. That doesn't mean the object will appear to be going slower - it will appear to start late and arrive late on its journey but the time taken will be the same so you would measure the same speed.
The frequency of light that you see will not be reduced, either, unless you are getting the doppler effect because the motion is away from you.

 

[Lightfuzz]

To be more specific, the speed of light is 299,792,458 m/s.

 

[sophiecentaur]

Oh, I'm sure you can be more accurate than that.

 

[f95toli]

Oh, I'm sure you can be more accurate than that.

No, you can't. The speed of light is defined to be exactly 299,792,458 m/s

(maybe you were joking, but I figured it was worth this out)

 

[sophiecentaur]

Which reminds me of a friend at School who told us he had calculated pi to 40 sig. figs.. We were very impressed until he showed us how he'd done it. He'd divided 22 by 7 and carried on till he done it to 39 places.

I bet he still wakes up in a sweat, some nights, remembering the withering reception he got from his 'best mates'.

 

[f95toli]

Amusing story...But what made you think of that?

 

[sophiecentaur]

sig figs

 

[DaveC426913]

Which reminds me of a friend at School who told us he had calculated pi to 40 sig. figs.. We were very impressed until he showed us how he'd done it. He'd divided 22 by 7 and carried on till he done it to 39 places.

I bet he still wakes up in a sweat, some nights, remembering the withering reception he got from his 'best mates'.

There's an hour he'll never get back!

 

[silentbob14]

yeah your reflection is kind of not only slower but also it's in the past ;]

 

[ejr]

This looks a new excuse for narcissism, oh sorry I was doing a physics experiment! I wasn't REALLY just staring at myself.

 

[map19]

You are all wrong. Unless you're in a vacuum with a front-silvered mirror.
Speed of light in air is 0.9997c
in the mirror glass it's about 0.66c.

read the classic SciFi by Bob Shaw where slow glass takes months or years to pass light.

 

[sophiecentaur]

yeah your reflection is kind of not only slower but also it's in the past ;]

Please explain why it will appear "slower".