The de-Broglie wavelength associated with a ball of mass \( 150\,\mathrm{g} \) traveling at \( 30.0\,\mathrm{m/s} \) would be
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → \( 1.47 \times 10^{-34}\,\mathrm{m} \)
The de Broglie wavelength of a moving body is \( \lambda = h/p \), where \( p = mv \) is its momentum.
\( m = 150\,\mathrm{g} = 0.150\,\mathrm{kg} \)
\( v = 30.0\,\mathrm{m\,s^{-1}} \)
\( h = 6.63\times10^{-34}\,\mathrm{J\,s} \)
\( \displaystyle \lambda = \frac{h}{mv} = \frac{6.63\times10^{-34}}{0.150 \times 30.0} = \frac{6.63\times10^{-34}}{4.5} = 1.47\times10^{-34}\,\mathrm{m} \)
The wavelength is far too small to be detected, which is why the wave nature of a macroscopic ball is never observed.
Note: This question is from NCERT (2026-27). NTA sets numerical questions from NCERT too, so do not ignore NCERT while practising numericals.
NCERT (2026-27):
Wave Nature of Matter – …
