Question

When a blackened bulb thermometer is moved beyond the red region of the visible spectrum, there is a rapid rise in the temperature. This is due to the presence of:

• A. Infrared radiations
• B. Ultraviolet radiations
• C. X-rays
• D. Radio waves

Hint:

Remember the order of the electromagnetic spectrum around visible light: Ultraviolet \(\rightarrow\) Visible (Violet to Red) \(\rightarrow\) Infrared. Infrared radiation is often called "heat radiation".

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
The question describes an experiment where a thermometer shows a temperature increase when placed in the region just beyond the red end of the visible light spectrum. We need to identify the type of electromagnetic radiation responsible for this heating effect.
Step 2: Detailed Explanation:
The visible spectrum of light consists of colors arranged from violet to red (VIBGYOR).
The region of the electromagnetic spectrum just beyond the red light has wavelengths longer than red light. This region is called the infrared region.
Infrared (IR) radiations are primarily responsible for the heating effect of sunlight. They are readily absorbed by most materials, causing an increase in the internal energy and temperature of the material.
A blackened bulb is used because black surfaces are good absorbers of all types of radiation, making the temperature change more noticeable.
Ultraviolet (UV) radiation is found beyond the violet end of the spectrum and has more energy per photon, but infrared radiation carries more of the sun's heat energy. X-rays and Radio waves are other parts of the electromagnetic spectrum, but they are not located adjacent to the red region and are not the primary cause of heating in this experiment.
Step 3: Final Answer:
The rapid rise in temperature beyond the red region is caused by the absorption of Infrared radiations.