VA charakteristics of LED - Measurement of Planck constant

Experimental Setup


We export measured data and process it in suitable software, eg. MS Excel. To determine Planck constant we need to read voltage of diode in switching direction. We proceed in following way. When the dependence of voltage on current is linear, we fit these values with linear regression. Then we read intersection of regressed line and x-axis (see graph - aqua line at LED 2, graph can be enlarged by clicking on picture) - and write this voltage in table.


VA charakteristics of LED


When we all values of voltage for all LEDs, then we can calculate Planck constant from relation
h = U*e* λ/c,
where U is intersection voltage, e is charge of electron, λ is wavelength of LED, c is speed of light. Absolute and relative error is calculated towards tabelled value h = 6,626*10-34 J*s.

Results of measurement