[afchick7689]

The question asks to calculate the energy of line 'd' of the Balmer series in the hydrogen spectrum and gives a value of the wavelength as equal to 4080 angstroms. I am lost with this one- is there a formula for calculating energy? Should i convert the angostroms into some other measure? Can anyone just point me in the right direction, please?

[Yggdrasil]

E = hf, where

E = energy of the photon
h = Planck's constant (~6.63x10^-34)
f = frequency of the photon

Frequency and wavelenght (l) are related by the formula:
fl = v,
where v is the speed of the wave (in the case of EM radiation in a vacuum, v=c).

[afchick7689]

ok that makes sense, so i converted the angstroms into meters:

4 080 angstroms = 408 nanometers
408 nm |             1m              = 4.08 x 10-7 m
            | 1 000 000 000 nm

but in order to find the value of f (frequency) i still need the speed of the wave (b/c frequency * wavelength = speed)... where do i get this from???

[xiankai]

i think he specified the speed as c.

[afchick7689]

ok so can someone check my work here-- are these units all correct??

Calculate the energy of line ‘d’ of the Balmer series in the hydrogen spectrum.  The value of the wavelength = 4080 angstroms.

4 080 angstroms = 408 nanometers
408 nm |             1m              = 4.08 x 10-7 m
            | 1 000 000 000 nm

E = hf where: E = energy of the photon
h = Planck's constant (6.626068 × 10-34 m2 kg / s)
f = frequency of the photon
Frequency (f) and wavelength (l) are related by the formula:
fl = v,
where v is the speed of the wave (v = c) (c = 299 792 458 m / s)

f * 4.08 x 10-7m = 299 792 458 m/s
f = 7.3479 Hz

E = ( 6.626068 × 10-34 m2 kg / s) * 7.3479 Hz
E = 4.87 x 10^-33 j