Infrared, visible and ultraviolet radiations/light have different properties. Which one of the following statements related to these radiations/light is not correct?
- A.The wavelength of infrared is more than that of ultraviolet radiation.
- B.The wavelength of ultraviolet is smaller than that of visible light.
- C.The photon energy of visible light is more than that of infrared light.
- D.The photon energy of ultraviolet is lesser than that of visible light.
Correct answer
Explanation
The correct answer is D. Ultraviolet photons carry more energy than visible light, not less, so this statement is wrong.
The energy of a photon is E = hc/λ, so a shorter wavelength means higher energy. In order of wavelength, infrared is longest (about 700 nm to 1 mm), visible light comes next (about 400 to 700 nm, red to violet), and ultraviolet is shorter still (about 10 to 400 nm). Photon energy therefore rises in the order infrared, visible, ultraviolet. This is why ultraviolet rays can tan or burn the skin and damage DNA, while infrared is felt mostly as heat.
A is correct, because infrared lies beyond red and has a longer wavelength than ultraviolet.
B is correct, because ultraviolet lies beyond violet and has a shorter wavelength than visible light.
C is correct, because visible light has a shorter wavelength and so higher photon energy than infrared.
Exam tip: wavelength and energy run opposite: radio, microwave, infrared, visible, UV, X-ray, gamma in rising energy.
Practice Questions
View allConsider the following actions :
1. Detection of car crash/collision which results in the deployment of airbags almost instantaneously
2. Detection of accidental free fall of a laptop towards the ground which results in the immediate turning off of the hard drive
3. Detection of the tilt of the smartphone which results in the rotation of display between portrait and landscape mode
In how many of the above actions is the function of accelerometer required?
- A.Only one
- B.Only two
- C.All three
- D.None
Show answer
An accelerometer measures acceleration, including the pull of gravity, and each of the three actions depends on reading it. An accelerometer is a small sensor, today usually a MEMS (micro-electro-mechanical system) chip, that senses changes in speed and the direction of gravity.
Read the full explanation →Consider the following statements :
1. Carbon fibres are used in the manufacture of components used in automobiles and aircrafts.
2. Carbon fibres once used cannot be recycled.
Which of the statements given above is/are correct?
- A.1 only
- B.2 only
- C.Both 1 and 2
- D.Neither 1 nor 2
Show answer
Carbon fibre is widely used in cars and aircraft for its strength and low weight, and it can be recovered and recycled.
Read the full explanation →Which one of the following cell organelles contains DNA?
- A.Golgi apparatus
- B.Mitochondrion
- C.Lysosome
- D.Endoplasmic reticulum
Show answer
Mitochondria carry their own small, circular DNA and their own ribosomes. Mitochondria are the powerhouses of the cell, where aerobic respiration makes ATP.
Read the full explanation →Which set of vegetables is underground stem or modified stem of a plant?
- A.Potato, artichoke, round gourd
- B.Onion, garlic, carrot
- C.Potato, onion, garlic
- D.Potato, garlic, turnip
Show answer
All three are underground modified stems: the potato is a stem tuber, and onion and garlic are bulbs. A stem can be told from a root by its nodes and buds.
Read the full explanation →A sound wave having frequency of 300 Hz is travelling in an unknown medium. Its wavelength is not known. It travels a distance equal to 150 times its wavelength in time t. The value of t is :
- A.0.5 s
- B.1 s
- C.1.5 s
- D.2 s
Show answer
A wave moves forward by one wavelength in each cycle, so 150 wavelengths take 150 cycles, and 150 cycles at 300 per second take half a second.
Read the full explanation →