We have to conduct a lab experiment for a photochemical reaction. We will be using a redand violet film and filter paper labeled 40W and 60W. On each piece of paper we will add 1 drop of NaCl and AgNO3 and then let it sit under a lamp to see what happens. At the end we will obtain a transmittance spectrum from a spectrophotometer which will have the wavelengths from 300-700nm. The question says to calculate the energies for the red and violet films and remember to convert nm to meters.

Question

We have to conduct a lab experiment for a photochemical reaction. We will be using a redand violet film and filter paper labeled 40W and 60W. On each piece of paper we will add 1 drop of NaCl and AgNO3 and then let it sit under a lamp to see what happens. At the end we will obtain a transmittance spectrum from a spectrophotometer which will have the wavelengths from 300-700nm. The question says to calculate the energies for the red and violet films and remember to convert nm to meters.

1nm=1 X 10^-9m

So that I can be prepared to do these calculations I was just wondering how I would go about finding the energy because I am not sure.

Answer 1

E = hc/wavelength.

E is in joules.
h is Planck's consant in J*sec
w = wavelength in m.

Answer 2

To calculate the energy for the red and violet films, you need to use the formula:

E = hc/λ

Where:
E is the energy of a photon in Joules (J)
h is the Planck's constant (6.626 x 10^-34 J·s)
c is the speed of light (2.998 x 10^8 m/s)
λ is the wavelength of light in meters (m)

First, you need to convert the wavelength from nanometers (nm) to meters (m). The conversion factor given is 1nm = 1 x 10^-9m. So, for example, if the wavelength is given as 400 nm:

λ = 400 nm = 400 x 10^-9m = 4 x 10^-7m

Now, you can use the formula above to calculate the energy. For the red film, you will use the given wavelength for red light, and for the violet film, you will use the given wavelength for violet light.

Let's say the wavelength for the red film is 650 nm:

Convert the wavelength to meters:
λ = 650 nm = 650 x 10^-9m = 6.5 x 10^-7m

Now, use the formula:
E(red) = hc/λ
E(red) = (6.626 x 10^-34 J·s) x (2.998 x 10^8 m/s) / (6.5 x 10^-7m)

Calculate the value for E(red) using a calculator.

Similarly, for the violet film, if the wavelength is given as 400 nm, you would convert it to meters (4 x 10^-7m) and then use the formula:

E(violet) = hc/λ
E(violet) = (6.626 x 10^-34 J·s) x (2.998 x 10^8 m/s) / (4 x 10^-7m)

Calculate the value for E(violet) using a calculator.

Note: The energy calculated using this formula is the energy per photon, as light is quantized in discrete packets called photons.