# Homework Help: X-rays and their wavelengths

1. Feb 7, 2006

### UrbanXrisis

X-ray tubes used by dentists can have voltages as high as 80kV to accelerate the elecrons to produce the X-rays. What is the most lowest wavelength that can be produced by such electons?

This problem seems almost too easy... i need a check

$$\lamba = \frac{1.24x10^3 V^{-1} nm}{80kV}$$

$$\lamba = 0.0155 nm$$

2. Feb 8, 2006

### Tide

Check the units in your expression.

3. Feb 8, 2006

### UrbanXrisis

i thought wavelengths were in nm? why do I get units of nm/v^2?

4. Feb 8, 2006

### inha

the numerator should be 1240eVnm

5. Feb 8, 2006

### UrbanXrisis

I am stil getting $$\lambda = 0.0155 nm$$

I used the formula $$\lambda=\frac{h*c}{80kV*e}$$

and I got the same results. am I doing this correctly?

6. Feb 8, 2006

### imabug

what Tide said. Look at your units. Carefully.

7. Feb 8, 2006

### UrbanXrisis

ignoring the first part, and using:

$$\lambda=\frac{h*c}{80kV*e}$$
(eV*s*m/s)/(V*m/s)

should it be in units of (eV*s)/V ?? shouldnt it be in meters?