# What is cutt off frequency

1. Feb 22, 2015

### Aafia

This term is new for me so explain it simply ... and give a simple definition about cutt off frequency

2. Feb 22, 2015

### DrGreg

Please give an example of where you have seen this.

If you've seen it on the internet, give a link, otherwise give the sentence i

3. Feb 22, 2015

Staff Emeritus
4. Feb 22, 2015

### Aafia

5. Feb 22, 2015

### Aafia

I have seen it in physics book chapter about light and the topic is photoelectric effect ..

6. Feb 22, 2015

### Staff: Mentor

Thanks.

So you probably know that when you shine light on a metal surface, it ejects electrons. As the frequency of the light increases, the maximum kinetic energy of the electrons increases. As the frequency of the light decreases, the maximum KE of the electrons decreases, and there is a certain frequency at which the maximum KE of the electrons becomes zero. Below that frequency, the photoelectric effect doesn't happen. We call that the "cutoff frequency."

In general, a word or phrase can be used on more than one context, with different meanings in each context. Furthermore, different authors may use the same word in different ways, even though they agree on the mathematics that goes along with it. That's why it's important to tell us what you're reading about, and where you read it, and whatever equations go along with it, if any.

In this case, I can imagine "cutoff frequency" also being used to describe some kinds of electrical circuits, e.g. radio tuners.

7. Feb 22, 2015

Thanks