High School Teachers
at CERN
WWW.CERN.CH

TEACHING MATERIALS

VISITING CERN

LINKS & BOOKS

HST
 

Measuring Planck's Constant using LEDs

 

LED colour

wavelength (nm)

frequency (Hz)

p.d. needed (V)

energy (J)

Blue

470

6.38x1014

2.38

3.81x10-19

Green

563

5.33x1014

1.69

2.70x10-19

Yellow

585

5.13x1014

1.63

2.61x10-19

Orange

620

4.84x1014

1.48

2.37x10-19

Red

650 

4.62x1014

1.47

2.35x10-19

c = 3.00x108 m/s
e = 1.60x10-19 C

 

From the slope of the graph Planck's Constant = 8.64x10-34 Js

 
© CERN and High School Teachers Programme at CERN

Last modified: 28 June 2002