# Dose E=hn means quantization of energy?

1. Feb 11, 2012

### athrun200

I have an example class yesterday, but one question troubled me.

In part (b), why does E=nhf?
For me, it seems E=nh is enough, why does the equation involve frequency f after quantization?

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2. Feb 11, 2012

### gomunkul51

One answer might be: The unit of E (energy) is a Joule, the unit of h (Plank's constant) is Joule time a second. If you want the equation to be correct you need to multiply h with something that has units of 1 over a second.

Roman.

3. Feb 11, 2012

### bcbwilla

What do you mean "E = nh is enough"? That equation is not correct, because as pointed out above, the units are not correct.

4. Feb 11, 2012

### derek101

h = energy per cycle.
f = number of cycles per unit of time.
your quantization must include a quantization of time.

5. Feb 11, 2012

### athrun200

Thanks! I have forgotten to consider the unit.

6. Feb 12, 2012

### questionpost

Energy within a single system is quantized, but there are different energies that result from following the E=nh model in different systems, so if you consider every possible system energy is continuous, just like the light spectrum.