how do you find wavelength from energy? PLEASE HELP!!!!!?

Question

I have no idea how to do these 2 problems!

1.) The energy of a photon is 2.87 x 10^-19 J. What is the wavelength of the corresponding light?

2.) Neutrons are used to obtain images of the hydrogen atoms in molecules. What energy must be imparted to each neutron in a neutron beam to obtain a wavelength of 8.4 pm? Obtain the energy in electron volts (eV). Hint: 1 eV=1.602 x 10^-19.

I'm pretty sure you do them both the same way, with 2 having a little more work... maybe. I really have no idea!

If anyone could give me a hint or explain how to do it or ANYTHING at all I'd REALLY appreciate it!! Thanks so much!!!!

Answer 1

a) E = hc/wavelength, h = 6.626*10-34 J •s, c = 10^8 m/s

wavelength = 6.626*10-34Js(10^8m/s)/
2.87*10-19J
= 2.3 *10-7 m * 10^9nm/m = 230.87 nm

b) 1 pm = 10-12 m

h = 4.136 * 10-15 eV•s

E = 4.136*10-15 eVs(10^8m/s)/8.4*10-12m = 49,238 eV

The smaller the wavelength the higher the energy

a neutron beam is VERY high energy!

Answer 2

The equation is:

E = hv. E is the energy in JOULES
h is the Planck constant: 6.626068 × 10-34 m2 kg / s
v is the frequency in Hz

Question 1:
E = 2.87 x 10^-19 J
E = hv, rearrange:
v = E/h = (2.87 x 10^-19 J)/(6.626068 × 10^-34 m2 kg / s)

2. Same principle:
E = hv = (6.626068 × 10-34 m2 kg / s) x v

Now, frequency is in Hz. This is 'cycles per second'
For EM radiation, c (the speed of light) = vw, where v is the frequency and w is the wavelength.


However, neutrons are massive particles and do not travel at the speed of light. You cannot determine the wavelength unless you know the speed of the neutrons. If you know the speed, then use E = hv, where
speed of neutron = vw, hence w = (speed of neutron)/v

Answer 3

1. E = hf
h = planck's constant, f = frequency

v = f*wavelenth
v = c = speed of light since it's a photon

2. Same principle, given the wavelength, solve for frequency and then plug into E = hf to find the energy in Joules. Divide by 1.609x10^-19 to get eV.

Answer 4

see in the first prob simply use the formula e=h*c\lambda(wavelenth)
h is the planck's constt=6.66*10^34
c=3*10^8m/s


in the sec probthe same thing isto be done.just rem that 1pm =1*10^-12 metres
and divide the ans with 1.602*10^-19

Answer 5

The magic formula is E = h nu, or E = h/lambda, where E is the energy, h is Planck's constant, nu is the frequency, and lambda is the wavelength. Planck's constant is 6.626E-34 joule-seconds.

Answer 6

First reaction is authentic. specifically, E = h nu = h c/lambda, the place h is Planck's consistent (6.6E-34), nu is frequency, lambda is wavelength, and c is the fee of sunshine.