# Science

posted by .

In black and white photography, a photon energy of about 4.00 x 10 to the negative 19th power I is needed to bring about the changes in the silver compounds used in the film. Explain why a red light used in a darkroom does not affect the film during developing.

• Science -

for red light λ=0.62 – 0.76 μm
max f=c/ λ=3•10⁸/0.62•10⁻⁶=4.84•10¹⁴ Hz
ε=hf=6.63•10⁻³⁴•4.84•10¹⁴ =3.2•10⁻¹⁹ J
Since 3.2•10⁻¹⁹ J < 4•10⁻¹⁹ J red light does not affect the film .

## Similar Questions

1. ### Physics

The frequency of violet light is about twice that of red light. How does the energy of a violet photon compare with the energy of a red photon?
2. ### Physics - light

1. Blue light and yellow light combine to produce white light because they constructively interfere. Explain why 2. You shine yellow light on an object and it appears black. What color might the object be if illuminated by red light?
3. ### Chemistry (Electrons in Atoms)

The wavelength of visible light varies from 0.40 μm to 0.70 μm as the color of the light changes from violet to red. Calculate the energy of a photon whose wavelength is 0.67 μm HINT: From the wavelength and the speed …
4. ### Physics

In black-and-white photography, a photon energy of about 4.00 x 10-19 J is needed to bring about the changes in the silver compounds used in the film. (a) What is the frequency of the light needed to bring about these changes?
5. ### Physics

In black-and-white photography, a photon energy of about 4.00 x 10-19 J is needed to bring about the changes in the silver compounds used in the film. (a) What is the frequency of the light needed to bring about these changes?
6. ### Chemistry

The equation for photon energy, , is where = 6.626×10−34 (Planck's constant) and = 3.00×108 (the speed of light). What is the wavelength, , of a photon that has an energy of = 3.99×10−19 ?
7. ### maths probability

a box contains 20 red,30 black,40 blue,50 white. what will be the minimum number of balls to be drawn without replacement so that you are certain about getting 4 red,5 black,6 blue,7 white balls?
8. ### photography

Which of the following is a good tip for documentary photography?
9. ### physics

A photon of light has a wavelength of about 600 nm (1nm = 1 x 10-9 m). What is the energy of this photon of light?
10. ### Physics (light)

A soap film is viewed in white light. If the film is much thinner than the wavelength of blue light, what is the appearance of the film?

More Similar Questions