The constituents of atomic nuclei are believed to be
1. neutrons and protons
2. protons only
3. electrons and protons
4. electrons, protons and neutrons
The half-life of radium is about 1600 yr. Of 100 g of radium existing now, 25 g will remain unchanged after
1. 4800 yr
2. 6400 yr
3. 2400 yr
4. 3200 yr
Half-life of a radioactive substance is 12.5 h and its mass is 256 g. After what time, the amount of remaining substance is 1 g?
1. 75 h
2. 100 h
3. 125 h
4. 150 h
A radioactive substance disintegrates 1/64 of initial value in 60 s. The half-life of this substance is
1. 5 s
2. 10 s
3. 30 s
4. 20 s
The nucleus absorbs an energetic neutron and emits a beta particle . The resulting nucleus is
1.
2.
3.
4.
If in a nuclear fusion process, the masses of the fusion nuclei be and the mass of the resultant nucleus be , then
1.
2.
3.
4.
The graph between the square root of the frequency of a specific line of the characteristic spectrum of X-rays and the atomic number of the target will be:
1. | |
2. | |
3. | |
4. |
The nuclei of which one of the following pairs of nuclei are isotones?
1.
2.
3.
4.
The counting rate observed from a radioactive source at t = 0 second was 1600 counts per second and at t = 8 seconds it was 100 counts per second. The counting rate observed, as counts per second, at t = 6 seconds will be:
1. 400
2. 300
3. 200
4. 150
If is the original mass of the substance of half life period = 5 years, then the amount of substance left after 15 years is
1. /8
2. /16
3. /2
4. /4