Visible light's wavelength range _________.
0.39 - 0.77 μm
Understanding the Visible Light Wavelength Range
Visible light is the segment of the electromagnetic spectrum that is detectable by the human eye. Like all forms of electromagnetic radiation, visible light travels in waves and can be characterized by its wavelength, frequency, or energy. The question asks for the typical wavelength range of visible light.
The Electromagnetic Spectrum
The electromagnetic spectrum encompasses a vast range of wavelengths and frequencies, from long radio waves to very short gamma rays. Visible light occupies a relatively narrow band within this spectrum, located between infrared radiation (longer wavelengths) and ultraviolet radiation (shorter wavelengths).
Wavelength and Common Units
Wavelength is the distance between successive crests or troughs of a wave. For light, wavelengths are typically measured in very small units. Common units used for light wavelengths include:
- Nanometer (nm): One billionth of a meter ($10^{-9}$ m).
- Micrometer ($\mu$m): One millionth of a meter ($10^{-6}$ m).
- Angstrom (Å): One tenth of a nanometer ($10^{-10}$ m).
Converting between these units is important. 1 $\mu$m = 1000 nm.
Typical Range for Visible Light
The widely accepted range for the wavelength of visible light is approximately 400 nanometers (nm) to 700 nanometers (nm). Different sources may give slightly varying ranges.
Let's convert this range to micrometers ($\mu$m):
- 400 nm = $400 \times 10^{-9}$ m = $0.4 \times 10^{-6}$ m = 0.4 $\mu$m
- 700 nm = $700 \times 10^{-9}$ m = $0.7 \times 10^{-6}$ m = 0.7 $\mu$m
So, the typical range is approximately 0.4 $\mu$m to 0.7 $\mu$m.
Analyzing the Given Options
Now let's look at the options provided and compare them to the known range:
- 0.39 - 0.77 mm: This range is in millimeters (mm). 1 mm = 1000 $\mu$m. So, 0.39 mm = 390 $\mu$m and 0.77 mm = 770 $\mu$m. This range (390-770 $\mu$m) is much larger than the visible light range (0.4-0.7 $\mu$m). This option is incorrect.
- 0.39 - 0.77 $\mu$m: This range is in micrometers ($\mu$m). The values 0.39 $\mu$m and 0.77 $\mu$m are very close to the standard 0.4 $\mu$m to 0.7 $\mu$m range. Converting to nanometers, this is 390 nm to 770 nm, which is a common representation of the visible spectrum range, extending slightly beyond the typical 400-700 nm. This option appears correct.
- 0.39 - 0.77 nm: This range is in nanometers (nm). The values 0.39 nm and 0.77 nm are extremely small. Visible light wavelengths are in the hundreds of nanometers (like 400-700 nm). This range is far too small and corresponds to X-rays or gamma rays. This option is incorrect.
- 0.39 - 0.77 cm: This range is in centimeters (cm). 1 cm = 10 mm = 10,000 $\mu$m. So, 0.39 cm = 3900 $\mu$m and 0.77 cm = 7700 $\mu$m. This range is extremely large and corresponds to radio waves or microwaves. This option is incorrect.
Conclusion: The Correct Wavelength Range
Based on the analysis of typical visible light wavelengths and unit conversions, the range 0.39 - 0.77 $\mu$m is the only plausible option that represents the wavelength range of visible light among those provided. This range, while slightly different from the commonly cited 0.4-0.7 $\mu$m or 400-700 nm, is well within accepted variations depending on the context or source.
Revision Table: Electromagnetic Spectrum Ranges
| Type of Radiation | Approximate Wavelength Range | Common Units |
|---|---|---|
| Radio waves | > 1 mm | meters, centimeters, millimeters |
| Microwaves | 1 mm - 1 meter | centimeters, millimeters |
| Infrared | 700 nm - 1 mm | micrometers ($\mu$m), millimeters (mm) |
| Visible light | 400 nm - 700 nm (Approx. 0.4 $\mu$m - 0.7 $\mu$m) |
nanometers (nm), micrometers ($\mu$m) |
| Ultraviolet | 10 nm - 400 nm | nanometers (nm) |
| X-rays | 0.01 nm - 10 nm | nanometers (nm), picometers (pm) |
| Gamma rays | < 0.01 nm | picometers (pm) |
Additional Information: Colors and Wavelengths
The visible light spectrum is further divided into different colors, each corresponding to a specific sub-range of wavelengths. From longer wavelengths to shorter wavelengths, the colors are typically remembered using the acronym ROYGBIV:
- Red: Longest wavelengths (approx. 620-750 nm or 0.62-0.75 $\mu$m)
- Orange: (approx. 590-620 nm or 0.59-0.62 $\mu$m)
- Yellow: (approx. 570-590 nm or 0.57-0.59 $\mu$m)
- Green: (approx. 495-570 nm or 0.495-0.57 $\mu$m)
- Blue: (approx. 450-495 nm or 0.45-0.495 $\mu$m)
- Indigo: (approx. 420-450 nm or 0.42-0.45 $\mu$m)
- Violet: Shortest wavelengths (approx. 380-420 nm or 0.38-0.42 $\mu$m)
The option range 0.39 - 0.77 $\mu$m (which is 390 - 770 nm) comfortably covers these individual color ranges, from violet to red.
Important Questions from Waves
If the frequency of a sound wave is 50 Hz, then what is its time period?
Hertz is the SI unit of ________.
A running race is organized between ultrasonics, audible and infrasonic waves in a medium, then the winner is:
When a light wave travels from air to water, then which property remain unchanged ?
- Wavelength and frequency of a radio wave are 12 m and 25 × 106 Hz respectively. Calculate its velocity.
