Consider the following statements about visible light, UV light and X-rays: 1. The wavelength of visible light is more than that of X-rays. 2. The energy of X-ray photons is higher than that of UV light photons. 3. The energy of UV light photons is less than that of visible light photons.
1 and 2 only
Understanding Visible Light, UV Light, and X-rays
This question asks us to compare the properties, specifically wavelength and photon energy, of visible light, ultraviolet (UV) light, and X-rays based on three statements. These are all types of electromagnetic radiation, differing primarily in their wavelength and frequency (and thus, energy).
The Electromagnetic Spectrum
The electromagnetic spectrum is a continuous range of all types of electromagnetic waves arranged according to frequency or wavelength. The relationship between energy (E), frequency (f), and wavelength ($\lambda$) of a photon is given by:
$$E = hf = \frac{hc}{\lambda}$$
where $h$ is Planck's constant and $c$ is the speed of light. This formula shows that energy is directly proportional to frequency and inversely proportional to wavelength. Therefore, waves with longer wavelengths have lower energy and lower frequency, while waves with shorter wavelengths have higher energy and higher frequency.
The order of these waves from longest wavelength (lowest energy) to shortest wavelength (highest energy) is:
- Radio waves
- Microwaves
- Infrared (IR)
- Visible light
- Ultraviolet (UV)
- X-rays
- Gamma rays
Based on this order, we can compare the properties of visible light, UV light, and X-rays.
Analyzing the Statements
Let's examine each statement:
Statement 1: The wavelength of visible light is more than that of X-rays.
- In the electromagnetic spectrum, visible light is located to the left of X-rays.
- Moving from left to right in the spectrum means decreasing wavelength.
- Therefore, visible light has a longer wavelength than X-rays.
This statement is correct.
Statement 2: The energy of X-ray photons is higher than that of UV light photons.
- In the electromagnetic spectrum, UV light is located to the left of X-rays.
- Moving from left to right in the spectrum means increasing energy (because wavelength decreases).
- Therefore, X-ray photons have higher energy than UV light photons.
This statement is correct.
Statement 3: The energy of UV light photons is less than that of visible light photons.
- In the electromagnetic spectrum, visible light is located to the left of UV light.
- Moving from left to right in the spectrum means increasing energy.
- Therefore, UV light photons have higher energy than visible light photons.
This statement is incorrect.
Summary of Properties
Let's summarize the relative positions and properties:
| Region | Position (Left to Right) | Relative Wavelength | Relative Energy |
|---|---|---|---|
| Visible Light | Left of UV and X-rays | Longest among the three | Lowest among the three |
| UV Light | Between Visible and X-rays | Shorter than Visible, Longer than X-rays | Higher than Visible, Lower than X-rays |
| X-rays | Right of Visible and UV | Shortest among the three | Highest among the three |
Conclusion
Based on our analysis of the electromagnetic spectrum and the properties of visible light, UV light, and X-rays:
- Statement 1 is correct (Wavelength of visible > Wavelength of X-rays).
- Statement 2 is correct (Energy of X-rays > Energy of UV light).
- Statement 3 is incorrect (Energy of UV light > Energy of visible light).
Therefore, only statements 1 and 2 are correct.
Revision Table: Electromagnetic Spectrum Properties
| Type of Wave | Wavelength Range (Approx) | Energy Range (Approx) |
|---|---|---|
| Visible Light | 400 - 700 nm | 1.8 - 3.1 eV |
| Ultraviolet (UV) | 10 - 400 nm | 3.1 - 124 eV |
| X-rays | 0.01 - 10 nm | 124 eV - 124 keV |
Note: The boundaries between regions are not sharp and can vary slightly depending on the definition.
Additional Information: Applications of Light and X-rays
- Visible Light: This is the part of the spectrum that the human eye can see. It's used for illumination, vision, photography, and fiber optics.
- UV Light: Has higher energy than visible light. It can cause sunburns and is used in sterilization, fluorescence, and medical treatments (like treating jaundice).
- X-rays: Very high energy waves that can penetrate soft tissues but are absorbed by denser materials like bone. They are widely used in medical imaging (X-rays scans), security screening, and material analysis.
Understanding the relative energies and wavelengths helps explain why these different types of radiation have such diverse effects and applications.
Important Questions from Electromagnetic Waves
Consider the two statements given below :
Statement-1: Infrared waves are also called heat waves.
Statement-2: Water molecules readily absorb infrared waves.
Select the correct answer using the code given below:
The wavelength of X-rays is of the order of
Which of the followings are the characteristics of electromagnetic waves?
1) They are elastic waves.
2) They can also move in a vacuum.
3) They have electric and magnetic components that are mutually perpendicular.
4) They move with a speed equal to 3 lakh meters per second.
Select the correct answer using the code given below:
Which of the following devices is based on the phenomenon of electromagnetic induction?
Which factor does NOT affect the magnitude of motional EMF in a conductor?
