Question

A. Calculate the energy of light that has a wavelength of
`8.45 x10^(-7)` m.

b. Red and green lights shine on an object. As shown, the green light bounces off, but the red light does not. Write two or more sentences to identify the wave interaction that each color of light has with the object. What color is the object?

c. Gamma rays and visible light are parts of the electromagnetic spectrum. Write three or four sentences to compare these electromagnetic waves with respect to the following properties: wavelength, energy, frequency, and speed.

Answer 1

a) E=hc/lambda=2.35*10^(-19) J or 1.47 eV

b) Since red is "consumed", it does not reflect to our eyes but disappears. Green reflects, so we see green color.

c) Being one part of the same spectrum, gamma rays may kill us, visible light pleases us. Why?

- Wavelength: gamma rays are shorter than visible.

- Energy: according to expression in a), gamma rays carry more energy.

- Frequency: according to f=c/lambda, visible light has lower frequency.

- Both travel at the speed of light.

Answer 2

PART A)

Energy of the light is given as

`E = (hc)/(\lambda)`

now we have

`\lambda = 8.45 * 10^(-7)m`

now we have

`E = (6.6 * 10^(-34) (3 * 10^8))/(8.45 * 10^(-7))`

now we have

`E = 2.34 * 10^(-19) J`

PART B)

When light of different wavelength interact with a given surface then surface has property to absorb the light of definite energy due to which that light is completely absorbed while other all energy is reflected back by the surface

Here same occur in the given example as here energy of green light is completely reflected by the surface while energy of red light is completely absorbed by the surface

PART C)

Wavelength = wavelength of gamma rays are less than the wavelength of visible light

Energy = energy of gamma rays are more than the energy of visible light

Frequency = frequency of gamma rays is more than the frequency of visible light

speed = speed of all electromagnetic waves are same so speed will be same for both