Does greater light intensity imply greater energy?

Click For Summary
SUMMARY

The discussion centers on the relationship between light intensity, energy, and brightness, particularly in the context of two stars at different distances. It establishes that light intensity increases with the number of photons and is inversely proportional to wavelength. The problem presented indicates that Star A radiates twice the energy of Star B but is also twice as far away, leading to confusion about which star appears brighter. The correct conclusion is that Star B appears brighter due to the inverse square law of brightness, which states that brightness decreases with the square of the distance from the source.

PREREQUISITES
  • Understanding of photon energy and light intensity
  • Familiarity with the inverse square law of brightness
  • Knowledge of wavelength and its relationship to energy
  • Basic principles of stellar luminosity and distance measurement
NEXT STEPS
  • Study the inverse square law in detail
  • Explore the concept of luminosity in astrophysics
  • Learn about the relationship between wavelength and energy in electromagnetic radiation
  • Investigate how distance affects observed brightness in astronomical observations
USEFUL FOR

Astronomy students, astrophysicists, educators in physics, and anyone interested in understanding the principles of light and energy in relation to stellar observations.

navalava
Messages
9
Reaction score
0
Since light intensity increases with the number of photons, and the photon can be viewed as energy, would energy be proportional to intensity of light? Also since energy is inversely proportional to the wavelength of light, this would mean that the intensity of light is also inversely proportional to the wavelength of light.

The reason I'm asking this is because I saw this problem:

Star A is radiating two times as much energy as Star B, but it
is two times the distance from us. Which star will appear
brighter, and by how much?

a. Star A will be 2 times brighter
b. Star B will be 2 times brighter
c. Star A will be 4 times brighter
d. Star B will be 4 times brighter
e. they will both have the same observed brightness

Since brightness increases with intensity of light, and intensity is proportional to energy, brightness should also be proportional to energy, which means that Star A would be 2 times brighter (if they are at equal distances). Since brightness is inversely proportional to distance, wouldn't both stars have the same observed brightness? But the answer is b., which I don't understand...I would really appreciate it if someone could clear this up for me. Thank you so much!
 
Science news on Phys.org
navalava said:
Since brightness is inversely proportional to distance...

Hint. Re-examine your assumptions.
 

Similar threads

Graduate Interference Intensity: Questions & Answers
  • · Replies 7 ·
Replies
7
Views
2K
Graduate What makes a light source "brighter"?
  • · Replies 7 ·
Replies
7
Views
5K
Undergrad Single-slit diffraction experiment and the conservation of energy
  • · Replies 20 ·
Replies
20
Views
3K
High School I still don't understand the propagation of light
  • · Replies 13 ·
Replies
13
Views
2K
Undergrad Why is Cherenkov radiation blue? And what about refractive index?
  • · Replies 3 ·
Replies
3
Views
2K
Undergrad Relation between spectral intensity and spectral energy density
  • · Replies 2 ·
Replies
2
Views
3K
Graduate Light intensity independant of frequency and E = hf
  • · Replies 10 ·
Replies
10
Views
2K
Undergrad Doubts about Fourier transform of IR spectroscopy
  • · Replies 3 ·
Replies
3
Views
2K
Undergrad The kinetic energy of proton-electron for a black body
  • · Replies 8 ·
Replies
8
Views
2K
Intensity of Stars and the Inverse Square Law Problem
  • · Replies 10 ·
Replies
10
Views
3K