Describe Rutherford's experiment to investigate the structure of the atom - Leaving Cert Physics - Question 9 - 2017

Rutherford concluded that atoms are composed of a small, dense, positively charged nucleus surrounded by electrons, which occupy the surrounding space, indicating that most of the atom is empty.

The Bohr model explains line spectra through the following process:

1. Energy is supplied to an atom, which excites its electrons.
2. The electrons transition to a higher energy level.
3. When the electrons fall back to their original energy level, they emit light at specific wavelengths, creating discrete spectral lines.

A labelled diagram of a spectrometer should include:

• Collimator
• Table
• Telescope
• Vapour lamp
• Filament bulb

(i) To observe a line spectrum, a light source (like a neon lamp) emits specific wavelengths that are diffracted through the grating, producing distinct lines on the spectrum.

(ii) In contrast, a continuous spectrum is observed when a light source (like a filament bulb) emits a broad range of wavelengths that are dispersed through the grating, resulting in a continuous color spectrum without distinct lines.

Using the formula:

$d = 3.33 imes 10^{-6} \ m$ $n \lambda = d \sin(\theta)$

Plugging in the values:

• For first line to left and right of the central image:
• $\theta = \arcsin \left( \frac{n \lambda}{d} \right)$
• For n=1, $\theta = \arcsin \left( \frac{1 \cdot 589 \times 10^{-9}}{3.33 \times 10^{-6}} \right)$
• The angular separation is calculated to be 20.4°.