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#physics history

4 public questions tagged with this topic.

Atomic Models - Rutherford, Thomson and Bohr

Why did Rutherford’s nuclear model fail to explain the stability of atoms?

**Thomson's plum pudding model** positive charge uniformly distributed in sphere with electrons embedded, positive charge spread, fails to explain large angle scattering observed. Bohr's model introduces stationary orbits with quantized angular momentum L = n h/2π, physical basis de Broglie standing wave condition 2πr = n λ, circumference fits n wavelengths, explains line spectrum. In classical theory, an accelerating electron (in circular orbit) emits radiation, losing energy and spiraling into the nucleus, contradicting atomic stability. Using E_n = -13.6/n² eV, r_n = n² a₀, L = n h/2π, R =

Ref: NCERT > Physics Book > Atoms and Nuclei > Atomic Models - Rutherford, Thomson and Bohr

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EM Wave Characteristics - Transverse Nature and E/B Ratio

What type of electromagnetic waves were produced and observed by Jagdish Chandra Bose in his experiments?

**Relationship E and B** in EM wave E₀ = c B₀, B₀ = E₀/c, for vacuum. Fields sustain each other via Maxwell's equations ∇×E = -∂B/∂t, ∇×B = μ₀ ε₀ ∂E/∂t, time-varying E produces B and vice versa, self-sustaining propagation without medium, speed c. The document mentions that J.C. Bose produced and observed electromagnetic waves with wavelengths of 25 mm to 5 mm , which fall in the microwave range. Using c = fλ, E₀/B₀ = c, I_d = ε₀ dΦ_E/dt, and spectrum classification λ = c/f, evaluation yields Microwaves, illustrating EM wave transverse nature and Maxwell's displacement current concept.

Ref: NCERT > Physics Book > Electromagnetic Waves > EM Wave Characteristics - Transverse Nature and E/B Ratio

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Applications of EM Waves in Communication and Medicine

What did Maxwell's unification of electricity, magnetism, and light lead to?

**X-rays and gamma rays in medicine** X-rays imaging because bone absorbs more than tissue, contrast, CT scan uses multiple X-ray projections, gamma knife uses focused gamma rays to destroy tumor with minimal surrounding damage, illustrating high-energy EM wave medical use. The document notes that Maxwell's work unified electricity, magnetism, and light, leading to the understanding that light is an electromagnetic wave and paving the way for technologies like radio communication. Using c = fλ, E₀/B₀ = c, I_d = ε₀ dΦ_E/dt, and spectrum classification λ = c/f, evaluation yields Understanding li

Ref: NCERT > Physics Book > Electromagnetic Waves > Applications of EM Waves in Communication and Medicine

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