Question

Which has the lower energy: red light or green light?

Short answer

Red light has lower energy than green light.

Step-by-step solution

Understanding Light Energy and Wavelength

Light energy is inversely proportional to its wavelength. This means longer wavelengths have lower energy and shorter wavelengths have higher energy.

Comparing Wavelengths of Red and Green Light

Red light has a longer wavelength compared to green light. The wavelength of red light ranges approximately from 620 to 750 nanometers, whereas green light ranges from 495 to 570 nanometers.

Applying the Proportionality of Energy to Wavelength

Since red light has a longer wavelength than green light, and knowing that energy is inversely related to wavelength, red light has lower energy than green light.

Key concepts

Wavelength

Wavelength is a fundamental concept in understanding light energy. It refers to the distance between consecutive peaks of a wave. In simpler terms, it is the 'length' of one full wave cycle.
Visible light, which is the light that we can see, has different colors because of varying wavelengths. For instance, red light has longer wavelengths than blue or green light, which results in its unique color.
Wavelength is measured in nanometers (nm). The visible spectrum ranges from about 400 nm to 700 nm, covering all the colors that we see. Each color has a specific range of wavelengths that give it its unique feel or hue. To visualize this, picture a rainbow where colors transition from violet (shorter wavelength) to red (longer wavelength).

• Short Wavelength: Higher Energy
• Long Wavelength: Lower Energy

Energy Inversely Proportional to Wavelength

The relationship between energy and wavelength is crucial in physics and helps us understand light behavior. Specifically, light energy is inversely proportional to its wavelength. This means that as the wavelength increases, the energy decreases, and vice versa.
Let's use the formula that illustrates this concept: \( E = \frac{h\cdot c}{\lambda} \)Where:

• \( E \) is the energy
• \( h \) is Planck's constant
• \( c \) is the speed of light
• \( \lambda \) is the wavelength

From this equation, you can see directly how energy decreases as wavelength \( \lambda \) increases because \( E \) is at the numerator while \( \lambda \) is at the denominator. This is an inverse relationship. It's a fundamental principle that helps explain why shorter-wavelength light, like violet, is more energetic than longer-wavelength light, such as red light.

Red Light Energy

Red light is a part of the visible light spectrum and is characterized by its longer wavelengths. Specifically, red light wavelengths range from about 620 to 750 nanometers.
Due to the inverse relationship between energy and wavelength, red light has lower energy compared to other visible light colors such as violet or green. This is why red light feels less intense and appears softer.
In practical applications, the lower energy nature of red light means it is often used in situations where high energy is not desirable. For example, red lights are used in night vision devices because it helps to preserve the dark adaptation of human eyes.

• Red Light Wavelength: 620 to 750 nm
• Red Light Energy: Lower compared to violet or blue light
• Application: Night vision, signaling, and in some medical applications

Understanding these properties enables us to make informed decisions about the use and impact of red light in various technologies and situations.