Question

Make a sketch representing the wave nature of light and label the wavelength. Suppose the sketch you just made corresponds to visible light. How would UV light be different? How would infrared light be different?

Short answer

Visible light can be sketched as a sinusoidal wave with labeled wavelength (λ). UV light would have a shorter wavelength (more waves in the same distance), and infrared light would have a longer wavelength (fewer waves in the same distance).

Step-by-step solution

Sketching a Wave

Draw a sinusoidal curve that oscillates above and below a central axis. This curve represents one cycle of a light wave. The peak represents the crest and the lowest point represents the trough.

Labeling Wavelength

Label the wavelength, which is the distance between two consecutive points that are in phase on the wave, such as from crest to crest or trough to trough. Mark the wavelength with an arrow or line and write 'Wavelength' or the symbol 'λ'.

Comparing to UV Light

To represent UV light, indicate that the waves would be closer together, or have a shorter wavelength, than the visible light wave you have sketched. This could be shown as additional waves within the same distance.

Comparing to Infrared Light

To depict infrared light, show that the waves would be further apart, or have a longer wavelength, than the visible light wave in your sketch. This would look like fewer waves across the same distance.

Key concepts

Wavelength

Imagine you are at the beach watching waves roll in. Each wave has a certain distance between one crest and the next. This distance is known as the wavelength. In the light spectrum, wavelength is the distance between consecutive points of the wave that are in phase. It is commonly denoted by the Greek letter lambda (\( \lambda \)).

Shorter wavelengths carry more energy and oscillate more frequently. The wavelength of light determines its color in the visible spectrum and its properties outside that range. For example, ultraviolet (UV) light has a shorter wavelength than visible light, which means it oscillates faster and carries more energy. This is why UV light can cause sunburn. On the other hand, infrared light has a longer wavelength and less energy, feeling warm to our skin but not causing immediate harm.

Visible Light

Let's focus on the colors you can actually see. Visible light is a part of the electromagnetic spectrum that human eyes can detect. It encompasses a range of wavelengths from approximately 380 nm to about 750 nm. Starting from violet, which has the shortest wavelength, the colors progress through blue, green, yellow, orange, and red, the latter having the longest wavelength within the visible spectrum.

When light hits objects, it can be absorbed, reflected, or transmitted, depending on the object's properties. The specific wavelengths that are reflected or transmitted back to our eyes determine the colors we perceive. A red apple, for instance, absorbs all colors of the spectrum except for red, which it reflects, and that's why it appears red to us.

Ultraviolet (UV) Light

Did you know that there is more to sunlight than what meets the eye? Ultraviolet (UV) light is one of those invisible components. UV light has wavelengths ranging from about 10 nm to 400 nm, shorter than those of visible light. Due to its high energy, UV light plays a critical role in various natural and technological processes.

While UV light is essential for the production of vitamin D in our skin and is used to sterilize surgical instruments, too much exposure can be harmful. It can cause sunburn and has been linked to skin cancer. This is primarily because UV light penetrates deeply into biological tissues and can damage DNA. Protection from UV light is important, and it's the reason we wear sunscreen and sunglasses.

Infrared Light

Sometimes you can feel the light even if you can't see it. Infrared (IR) light has wavelengths longer than visible light, ranging from about 750 nm to 1 mm. It is perceived as heat rather than light. For example, when you feel the warmth of the sun without actually seeing the light, you're experiencing infrared radiation.

Infrared technology has many practical applications, including thermal imaging, which allows us to see heat differences in objects and beings, and remote controls for electronic devices. While infrared light does not pose the same risks as ultraviolet light, intense infrared radiation can cause burns. This spectrum of light is essential for astronomers who use it to study celestial bodies that are too cool to emit visible light but are still emitting heat.