hc = 1242eV nm. how ?

h ki value toh 6.636 smthng h fer yhan kya li h apne ?

Here we assume than h_c is the Planck's constant.

The value of the Planck's constant in electron volts is 4.135 x 10^-15 eV.s and its standard value (in Joules) is 6.626 x 10^-34 J.s. It is just a different way to express a physical, by changing its units.

Not sure where h_c = 1242 eV.nm came about. Could you please send the link of the page where you encountered this? It will help us explaining it better.

Thanks !