Physics - Study Mode

[#586] Which layer of the earth's atmosphere reflect back the radio waves to the earth's surface ?
Correct Answer

(A) Ionosphere

Explanation

Solution: Ionosphere reflect back the radio waves to the earth's surface.

[#587] Where are mesons found ?
Correct Answer

(A) Cosmic rays

Explanation

Solution: Mesons are not produced by radioactive decay, but appear in nature only as short-lived products of very high-energy interactions in matter, between particles made of quarks. In cosmic ray interactions, for example, such particles are ordinary protons and neutrons. Mesons are hadronic subatomic particles composed of one quark and one anti-quark, bound together by the strong interaction. Because mesons are composed of sub-particles, they have a physical size, with a radius roughly one femtometre, which is about 2/3 the size of a proton or neutron. All mesons are unstable, with the longest-lived lasting for only a few hundredths of a microsecond. Charged mesons decay (sometimes through intermediate particles) to form electrons and neutrinos.

[#588] Who discovered X-ray?
Correct Answer

(C) Wilhelm Roentgen

Explanation

Solution: Wilhelm Roentgen discovered X-ray.

[#589] Which of the following has the lowest frequency?
Correct Answer

(A) Visible light

Explanation

Solution: The electromagnetic spectrum is generally divided into seven regions, in order of decreasing wavelength and increasing energy and frequency: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays and gamma rays.So among the given options, visible lights has the lowest frequency, while gamma rays has the highest.

[#590] Which of the following is not true about X-rays?
Correct Answer

(A) Have low penetrating power

Explanation

Solution: X-rays and gamma rays are photons, i.e. high energy light-waves. When emitted by a source, for example, radium or cobalt, located outside the body, they easily pass through the body, hence they are usually called penetrating radiation. Because X-rays are penetrating, they can be used in diagnostic medicine to image human bones or human organs made opaque by a dye.