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The relation between the wavelength of electromagnetic radiation (λ) and the de Broglie wavelength of its quantum (photon) (λ') is ________.

Asked in GUJCET 2026 · Matter wave against photon

• (1) λ' > λ
• (2) λ' < λ
• (3) λ' = λ
• (4) λ' = λ/2

Step-by-step solution

Why the other options are wrong

• (1) A photon's momentum is exactly p = h/λ, so λ' = h/p hands λ straight back and cannot come out larger. A larger λ' would mean the photon carried less momentum than h/λ.
• (2) Nothing shortens it either: substituting p = h/λ into λ' = h/p returns exactly λ. This option imagines the matter wave of a photon as something finer than the radiation itself.
• (4) Uses the momentum a photon delivers when it bounces straight back off a surface, (2E)/c, as the photon's own momentum; that halves the answer to h/p = λ/2. The factor of two belongs to the reflection, not to the photon, whose momentum is E/c.

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