Which of the following representations is correct for an atom X with 28 electrons and 30 neutrons?
\(^{30}_{28} X\)
\(^{28}_{30} X\)
\(^{58}_{30} X\)
\(^{58}_{28} X\)
Correct answer is D
\(X^{A = p + n = 28 + 30 = 58}_{Z = P = E = 28}\)
49.6g
37.2g
24.8g
12.4g
Correct answer is A
\(1 \to \frac{1}{2} \to \frac{1}{4} \to \frac{1}{8} \to \frac{1}{16} \to \frac{1}{32}\)
\(\frac{1}{32} = 1.55g\)
1 = 1.55 x \(\frac{32}{1} = 49.6g\)
Which of the following statements about X-rays is not correct? They
are electromagnetic waves
can be used to study crystal lattice
can destroy living cells
are produced from the nucleus of an atom
Correct answer is D
No explanation has been provided for this answer.
In which of the following devices is the principle of photoelectric effect not applicable?
close-circuit television camera
burglar alarm
solar cells
periscope
Correct answer is D
No explanation has been provided for this answer.
An atom is normally electrically neutral because the
number of electrons is equal to the number of protons
number of electrons is equal to the number of neutrons
number of protons is equal to the number of neutrons
electrons of the atom are buried deeply in the nucleus
Correct answer is A
No explanation has been provided for this answer.