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Describe Rutherford's experiment to investigate the structure of the atom - Leaving Cert Physics - Question 9 - 2017
Question 9
Describe Rutherford's experiment to investigate the structure of the atom. What conclusions about the nature of the atom did Rutherford make? One of his stude... show full transcript
Worked Solution & Example Answer:Describe Rutherford's experiment to investigate the structure of the atom - Leaving Cert Physics - Question 9 - 2017
Step 1
Describe Rutherford's experiment to investigate the structure of the atom.
Answer
Rutherford's experiment involved directing alpha particles at a thin foil made of gold. Most of the alpha particles passed straight through the foil, indicating that atoms are mostly empty space. Some particles were deflected at various angles, and a small fraction rebounded directly. This led to the conclusion that atoms contain a small, dense, positively charged core (nucleus) surrounded by a cloud of electrons.
Step 2
What conclusions about the nature of the atom did Rutherford make?
Answer
Rutherford concluded that the atom is predominantly empty space with a dense, positively charged nucleus at its center. This core contains most of the atom's mass, while electrons orbit the nucleus in a relatively sparse arrangement.
Step 3
Explain, using the Bohr model, how line spectra are formed.
Answer
In the Bohr model, electrons occupy specific energy levels around the nucleus. When energy is supplied to an atom, electrons can absorb that energy and move to a higher or excited energy level. Once in this excited state, electrons will eventually fall back to their original energy levels. During this transition, they emit light of specific wavelengths, contributing to the emission line spectra characteristic of each element.
Step 4
Draw a labelled diagram of a spectrometer and describe how a spectrometer and diffraction grating can be used to observe (i) a line spectrum.
Answer
A labelled diagram of a spectrometer includes: the collimator, table, telescope, and light source (vapor lamp). A line spectrum can be observed by using a spectrometer with a diffraction grating to separate light from a gaseous element. When the light passes through the grating, it produces distinct lines on the spectrum that correspond to the specific wavelengths emitted by the element.
Step 5
(ii) a continuous spectrum.
Answer
To observe a continuous spectrum, the same spectrometer can be utilized, but with a filament bulb as the light source. The light does not produce distinct lines; instead, it spreads out into a continuous range of wavelengths, producing a full spectrum of colors.
Step 6
Calculate the angular separation between the first line to the left of the central image and the first line to the right of the central image.
Answer
Using the formula for angular separation in a diffraction grating:
d = n imes ext{sin}( heta)
where:
- d = distance between lines on the grating = 3.33 × 10^{-6} m,
- n = order of diffraction (1 for first order),
- heta = angle of diffraction.
Given the wavelength λ = 589 nm = 589 × 10^{-9} m:
Calculating for angular separation:
a = 2 imes heta,
ext{where } heta = ext{sin}^{-1} rac{n ext{λ}}{d} = ext{sin}^{-1} rac{589 imes 10^{-9}}{3.33 imes 10^{-6}} = 10.2^ ext{o}
Thus, the angular separation is:
angular separation = 20.4^ ext{o}.