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# what are light gates?????? watch

1. I'm doing physics as level, and I am revising and LIGHT GATES has come up... What is it? How do they work? What do they measure??? I am clueless. Please help! Many thanks.
2. Detectors. They detect when something goes through them and how long it takes to cross.
The light gate has a beam going from one LED/IR light source onto a detector. As something goes through it, the beam is "Cut".
The light gate measure how long the beam has been cut for. That gives you a measure for time.
Some light gates will allow you to plug in the length of the crossing object, and then it'd automatically calculate:
Length of object/time = How fast it was travelling.
3. (Original post by tamimi)
Detectors. They detect when something goes through them and how long it takes to cross.
The light gate has a beam going from one LED/IR light source onto a detector. As something goes through it, the beam is "Cut".
The light gate measure how long the beam has been cut for. That gives you a measure for time.
Some light gates will allow you to plug in the length of the crossing object, and then it'd automatically calculate:
Length of object/time = How fast it was travelling.
I can't thank you enough! +ve rep for you.
4. (Original post by sharmine)
I can't thank you enough! +ve rep for you.
Merci Buckets.
5. my name is jeff
6. what unit do they measure in?
7. (Original post by 2221)
what unit do they measure in?
metres per second. The unit of speed.
8. (Original post by 2221)
what unit do they measure in?
(Original post by Iluv2edgedsword)
metres per second. The unit of speed.
Hi both This is an old thread - please try and create new ones if you want to ask a question.

Going to close this now.

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