Select the correct answer.

Fred points a toy laser gun at a wall. Considering that the frequency of the gun's light is [tex]4.91 \times 10^{14}[/tex] hertz and that Planck's constant is [tex]6.61 \times 10^{-34}[/tex] joule-seconds, what is the energy of the laser light?

A. [tex]3.24 \times 10^{-19}[/tex] joules
B. [tex]4.91 \times 10^{15}[/tex] joules
C. [tex]204 \times 10^{-21}[/tex] joules
D. [tex]4.92 \times 10^{-18}[/tex] joules



Answer :

To solve this problem, we need to use the formula for the energy of a photon, which is given by:

[tex]\[ E = h \cdot f \][/tex]

where:
- [tex]\( E \)[/tex] is the energy of the photon,
- [tex]\( h \)[/tex] is Planck's constant,
- [tex]\( f \)[/tex] is the frequency of the light.

Given values:
- Frequency ([tex]\( f \)[/tex]) of the gun's light: [tex]\( 4.91 \times 10^{14} \)[/tex] hertz,
- Planck's constant ([tex]\( h \)[/tex]): [tex]\( 6.61 \times 10^{-34} \)[/tex] joule-seconds.

Let's calculate the energy step-by-step.

1. Multiply the frequency [tex]\( f \)[/tex] by Planck's constant [tex]\( h \)[/tex]:

[tex]\[ E = 6.61 \times 10^{-34} \, \text{Joule-seconds} \times 4.91 \times 10^{14} \, \text{Hertz} \][/tex]

2. Performing the multiplication:

[tex]\[ E \approx (6.61 \times 4.91) \times (10^{-34} \times 10^{14}) \, \text{Joules} \][/tex]

[tex]\[ E \approx 32.43 \times 10^{-20} \, \text{Joules} \][/tex]

3. Simplifying the expression:

[tex]\[ E \approx 3.2451 \times 10^{-19} \, \text{Joules} \][/tex]

The value we found is approximately [tex]\( 3.2451 \times 10^{-19} \)[/tex] Joules.

Now, let's compare this value with the given options:

A. [tex]\( 3.24 \times 10^{-19} \)[/tex] Joules
B. [tex]\( 4.91 \times 10^{15} \)[/tex] Joules
C. [tex]\( 204 \times 10^{-21} \)[/tex] Joules
D. [tex]\( 4.92 \times 10^{-18} \)[/tex] Joules

The closest option to [tex]\( 3.2451 \times 10^{-19} \)[/tex] Joules is:

A. [tex]\( 3.24 \times 10^{-19} \)[/tex] Joules

Thus, the correct answer is:

A. [tex]\( 3.24 \times 10^{-19} \)[/tex] Joules.