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Solved problems for the chapter:

Infrared

View the theory »

Introduction to Light

1. Speed of light

2. Wavelength and frequency of light

3. Sources of light

3.1. Light sources based on black body radiation

3.2. Light emission due to changes in the energy levels of atoms

4. Luminous intensity and illuminance

5. Light perception

6. Forum

↓ Show theory [1] ↓

Detailed solution steps are available at:

https://en.openprof.com/wb/chapter:infrared/3615/

Example 1.

Which radiation has a lower frequency than infrared?

radio waves
red light
ultraviolet
X-rays

Example 2.

Which statement is correct?

A remote controller emits microwave radiation.
A remote controller emits infrared radiation.
A remote controller emits ultrasound.
A remote controller emits ultraviolet radiation.

Which row gives the approximate speeds at which infrared waves travel in air and in a vacuum?

	speed in air ()	speed in a vacuum ()
A
B
C
D

The two devices shown use different types of electromagnetic waves.

Which types of waves are used in these devices?

	medical scanning	remote controller
A	ultraviolet	infrared
B	ultraviolet	microwaves
C	X-rays	infrared
D	X-rays	microwaves

Thermal radiation is part of the electromagnetic spectrum. What is the name of this region of the spectrum?

gamma rays
infrared rays
ultraviolet rays
visible light rays

Visible light has a frequency of approximately . M and N are two other types of electromagnetic radiation.

The frequency of M is .

The frequency of N is .

Which types of radiation are M and N?

	M	N
A	radio waves	infrared
B	infrared	ultraviolet
C	ultraviolet	X-rays
D	X-rays	microwaves

The diagram shows typical wavelengths (in metres) of radio waves, microwaves, and X-rays in the electromagnetic spectrum. In which region are the waves used in TV remote controllers found?

Two students are describing different types of electromagnetic radiation.

student 1: This radiation is used in communication.

student 2: This radiation is used in remote controllers.

Which row shows the possible type of radiation that each student is describing?

	student 1	student 2
A	microwave	infrared
B	radio	ultraviolet
C	sound waves	visible light
D	X-rays	gamma rays

A student is asked to give two uses of four different types of electromagnetic radiation. In which row are both the uses correct?

	radiation	use 1	use 2
A	radio	sterilising medical equipment	mobile phone masts
B	microwaves	mobile phone	sterilising medical equipment
C	infrared	remote controllers	intruder alarms
D	X-rays	security in airports	intruder alarms

10.

What is the speed of infrared in air?

11.

The Sun emits infrared radiation and light. Light from the Sun reaches the Earth in 8 minutes. Which row gives correct information about the infrared radiation?

	wavelength of infrared radiation	time taken for infrared radiation to reach the Earth
A	longer than wavelength of light	8 minutes
B	longer than wavelength of light	much less than 8 minutes
C	shorter than wavelength of light	8 minutes
D	shorter than wavelength of light	much less than 8 minutes

12.

Which part of the electromagnetic spectrum is used by a remote controller for a television?

infrared waves
microwaves
radio waves
visible light

13.

Which statement about infrared radiation is not correct?

It travels at in a vacuum
It transfers energy
It travels at in air
It is a transverse wave

14.

Microwaves, green light, and infrared are three types of electromagnetic radiation. What is their order when listed by wavelength from the shortest wavelength to the longest?

15.

Which list shows regions of the electromagnetic spectrum in order of increasing frequency?

X-ray ultraviolet visible light infrared
X-ray infrared visible light ultraviolet
infrared visible light ultraviolet X-ray
ultraviolet visible light infrared X-ray

16.

Which row is correct?

	frequency of infrared waves compared to microwaves	use of infrared waves
A	greater	radiant heater
B	greater	satellite television
C	lower	radiant heater
D	lower	satellite television

17.

The frequency of an infrared wave is . What is the wavelength of this infrared wave?

18.

Radiation from which part of the electromagnetic spectrum is used in the remote controller for a television?

microwaves
radio waves
ultraviolet waves
infrared waves

19.

Which type of radiation does a remote controller use to send its instructions to a TV set?

gamma rays
infrared radiations
ultraviolet radiations
X-rays

20.

The diagram shows three types of electromagnetic radiation listed in a particular order. The electromagnetic radiation is travelling in a vacuum.

Which quantities increase in magnitude going from left to right across the list?

frequency only
neither speed nor frequency
speed and frequency
speed only