Modern Physics - Study Mode

[#151] In an observation, α-particles, β-particles and γ-rays have same energies. Their penetrating power in a given medium in increasing order will be
Correct Answer

(A) α, β, γ

[#152] The half-life of a radioactive element is 5 years, then the fraction of the radioactive substance that remains after 20 years is
Correct Answer

(D) $$frac{1}{16}$$

Explanation

Solution: The fraction of a radioactive substance that remains after a certain time period is given by the formula: Fraction remaining = (1/2)^(time elapsed / half-life) Given that the half-life of the radioactive element is 5 years and we want to find the fraction remaining after 20 years, we substitute these values into the formula: Fraction remaining = (1/2)^(20 / 5) = (1/2)^4 = 1/16 So, after 20 years, only 1/16 of the radioactive substance remains.

[#153] The function of heavy water in a nuclear reactor is to
Correct Answer

(A) Slow down the speed of neutrons

[#154] Size of nucleus is of the order of
Correct Answer

(B) 10 -15 m

[#155] Nuclear forces are
Correct Answer

(A) short ranged attractive and charged independent