Question

What are the basic SI units for (a) the wavelength of light, (b) the frequency of light, (c) the speed of light?

Short answer

The basic SI units for the properties of light are: (a) the wavelength of light is measured in meters (m); (b) the frequency of light is measured in Hertz (Hz), which is equal to 1/s; and (c) the speed of light is measured in meters per second (m/s).

Step-by-step solution

(a) Wavelength of Light

The wavelength of light is a measure of the distance between two consecutive points of the same phase (e.g., crests) in a wave. The basic SI unit for length or distance is the meter (m). Therefore, the basic SI unit for the wavelength of light is the meter (m).

(b) Frequency of Light

Frequency refers to the number of wave cycles (or oscillations) that pass through a given point in a unit of time. The basic SI unit for time is the second (s). Therefore, the basic SI unit for the frequency of light is the reciprocal of time, which is per second or Hertz (Hz). That is, 1 Hz = 1/s.

(c) Speed of Light

The speed of light is the rate at which light waves propagate through space. Since speed is a measure of distance traveled per unit of time, the basic SI unit for the speed of light is the division between the units for distance and time. Therefore, the basic SI unit for the speed of light is meters per second (m/s). In summary, the basic SI units for the given properties of light are: (a) meter (m) for the wavelength of light, (b) Hertz (Hz) for the frequency of light, and (c) meters per second (m/s) for the speed of light.

Key concepts

Wavelength of Light

The wavelength of light represents the distance between two identical points on consecutive waves, like crests or troughs.
In simpler terms, it measures how long each wave is from start to finish. In the SI system, the unit for this length is the meter (m).
The meter gives us a standard to measure lengths and distances, so knowing a light wave’s wavelength in meters helps us understand its size.

• A longer wavelength means lower energy.
• A shorter wavelength means higher energy.

Whether it’s visible light we can see or other types invisible to our eyes, using meters helps scientists describe and compare them easily.

Frequency of Light

Frequency describes how often waves pass a point in a given time frame.
This concept is like counting how many times a wave "hits" per second. In the SI unit system, frequency is measured in Hertz (Hz).
One Hertz means one cycle per second, so 50 Hz would mean 50 wave cycles each second.

• High frequency: More waves, higher energy.
• Low frequency: Fewer waves, lower energy.

This unit helps us understand the wave activities and how they relate to different energies and types of light.

Speed of Light

The speed of light refers to how fast light travels through space.
Think of it as the ultimate cosmic speed limit!
In the SI system, the unit is meters per second (m/s), which combines how far light travels (meters) with how quickly it gets there (per second).

• Light travels at approximately 299,792,458 m/s in a vacuum.
• This speed can change when light passes through different materials like air or water.

Knowing the speed of light helps us understand many phenomena in physics and helps us measure time and distance in space.

Meter

The meter is the foundational unit of distance in the International System of Units (SI).
It's widely used to measure length, height, and depth.
Defined as the distance light travels in a vacuum in 1/299,792,458 of a second, this precise measurement allows for accurate science and engineering work.

• 1 kilometer (km) equals 1,000 meters.
• 1 centimeter (cm) equals 0.01 meters.

This uniform unit helps scientists around the world to communicate and collaborate without confusion.

Hertz

Hertz (Hz) is the SI unit for frequency.
Named after Heinrich Hertz, it's used to quantify how often an event occurs per second.
In the context of light and sound waves, Hertz tells us how frequent wave cycles are.

• Mainly used in measuring electromagnetic waves, including light.
• Also applicable in the field of sound and radio activities.

Understanding Hertz helps us grasp the behavior and characteristics of different waves and their interactions.