Step 1: Understanding de-Broglie’s Hypothesis
Louis de-Broglie proposed that particles such as electrons could exhibit wave-like behavior.
He derived the equation for the de-Broglie wavelength \( \lambda \), which is given by:
\[
\lambda = \frac{h}{p}
\]
Where:
\( \lambda \) is the de-Broglie wavelength,
\( h \) is Planck's constant,
\( p \) is the momentum of the particle.
Step 2: Explanation of Other Options
Option (b) is incorrect because it represents a sum of \( h \) and \( p \), which is not the correct de-Broglie expression.
Option (c) is incorrect because it represents a difference between \( h \) and \( p \), which is also incorrect.
Option (d) repeats option (a), which is correct.
Step 3: Conclusion
Thus, the correct de-Broglie expression is \( \lambda = \frac{h}{p} \).