Short Answer

A spectrum is the band of different colours or wavelengths that appear when white light is separated into its components. This separation happens when light passes through a prism, raindrops, or any transparent medium. The colours in a spectrum always appear in a fixed order—violet, indigo, blue, green, yellow, orange, and red.

Spectra are not limited to visible light. Other types of waves like infrared, ultraviolet, X-rays, and radio waves also form spectra. Spectrums help scientists study light, stars, materials, and many physical properties of substances.

Detailed Explanation :

Spectrum

A spectrum is a range or spread of colours, wavelengths, or frequencies that appears when light or any other wave is separated into its components. The most familiar spectrum is the visible spectrum, which shows the seven colours of white light: violet, indigo, blue, green, yellow, orange, and red (VIBGYOR). When white light passes through a prism or raindrop, it bends and splits into these colours, forming a beautiful band known as the spectrum.

The concept of spectrum is important in many areas of science because it helps us study the nature of light and other electromagnetic waves. Every wave has its own wavelength and frequency. When these waves are separated based on their properties, they form a spectrum. Scientists use this to learn about stars, atoms, gases, and various materials.

How a Spectrum is Formed

A spectrum is formed due to the bending and splitting of light. When white light enters a transparent medium such as glass or water, it undergoes refraction. Each colour bends by a different amount because every colour has a different wavelength. Violet has the shortest wavelength and bends the most, while red has the longest wavelength and bends the least.

Due to this unequal bending, the seven colours spread out and form a band. This band of colours is called the visible spectrum. The order of colours remains the same because the bending depends on wavelength.

The formation of a spectrum explains why:

• A prism creates colourful patterns
• Rainbows form in the sky
• CDs or soap bubbles show shining colours

All these effects occur because light waves separate into different wavelengths.

Types of Spectra

Although the visible spectrum is the most familiar, there are many types of spectra used in physics. These can be broadly classified into:

1. Continuous Spectrum
   This type contains all wavelengths in a continuous sequence. There are no gaps.
   Example: Sunlight or light from a glowing filament bulb.
2. Emission Spectrum
   This spectrum shows bright coloured lines on a dark background. It is produced when atoms emit light at specific wavelengths.
   Example: Spectrum of hydrogen gas.
3. Absorption Spectrum
   This spectrum shows dark lines on a bright background. It is formed when a continuous spectrum passes through a material that absorbs certain wavelengths.
   Example: Solar spectrum when viewed through a spectroscope.

Spectra from stars and gases help scientists identify the elements present in them. Every element has its own unique pattern of lines, like a fingerprint.

Spectrum Beyond Visible Light

The spectrum is not limited to the colours we can see. The electromagnetic spectrum is a much larger range that includes many types of waves:

• Radio waves
• Microwaves
• Infrared rays
• Visible light
• Ultraviolet rays
• X-rays
• Gamma rays

Each type has different wavelengths and uses. For example:

• Radio waves help in communication
• Infrared is used in remote controls
• Ultraviolet helps in sterilisation
• X-rays are used in medical imaging
• Gamma rays help in cancer treatment

This extended spectrum helps in studying physical, chemical, and biological processes.

Importance of Spectrum

Spectrum plays a major role in science and technology. Some key applications include:

1. Studying Stars and Planets
   Astronomers examine the spectrum of starlight to know the star’s temperature, elements, speed, and distance.
2. Identifying Elements
   Each element gives a unique spectral pattern. Scientists use spectra to detect chemicals in laboratories and industries.
3. Optical Instruments
   Spectrometers and prisms use spectra for analysis and measurement.
4. Medicine and Imaging
   X-ray and gamma-ray spectra help in medical diagnosis and treatment.
5. Communication Technology
   Radio and microwave spectra are used in TV, mobile phones, and satellites.

Spectrum in Daily Life

Even in our daily life, we see spectra in many forms:

• Colours in a rainbow
• Patterns on soap bubbles
• Shining colours on a CD
• Reflected colours from oil on water

These are all small examples of dispersion and spectrum formation.

Conclusion

A spectrum is a band of colours or wavelengths formed when light or waves are separated into their components. The visible spectrum contains seven colours, while the full electromagnetic spectrum includes many types of waves. Spectra help scientists understand materials, stars, and various natural phenomena. Understanding the spectrum is an important part of optics and modern science.