Question

The temperature of the sun is measured with
A. Platinum thermometer
B. Gas thermometer
C. Pyrometer
D. Vapour pressure

Answer 1

An instrument is used to measure the temperature of the sun. It measures the radiation from the body whose temperature is measured. It compares brightness and takes colour variation to measure the temperature.

Complete answer: 1. Platinum Thermometer: Platinum Thermometer is a device that has a piece of platinum wire which determines the temperature by measuring the electrical resistance of the wire. Its principle of measurement is as the temperature changes, the resistance of the platinum wire also changes. Its measurement range is between $- 200^\circ C$ and $1000^\circ C$.
2. Gas Thermometer: Gas Thermometer is a thermometer that measures temperature when there is a change in volume or pressure of the gas. These thermometers have a range from $- 183^\circ C$ to $100^\circ C$.
3. Pyrometer: Pyrometers are non-contact thermometers that are used to measure the temperature of an object’s surface. This temperature depends on the radiation emitted from the object. The radiation can be either infrared or visible. It can measure temperature nearly up to $4000^\circ C$.
4. Vapour Pressure: There are vapour pressure thermometers that use a pressure gauge to measure vapour pressure of a liquid. The range of these thermometers is from $- {183^\circ }C$.
As we know, the temperature of the sun is very high, so we cannot get close to it. Hence, we need such an instrument which measures the temperature without getting in contact with it. So, a pyrometer can be used to measure the temperature of the sun.
Hence, the answer is option C-Pyrometer.

Note: Pyrometer is also known as an infrared thermometer or radiation thermometer or non-contact thermometer. There are different types of pyrometers such as colour pyrometer, high-speed pyrometer etc.