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Read the following passage and answer the accompanying questions - Leaving Cert Physics - Question 11 - 2016
Question 11
Read the following passage and answer the accompanying questions. The story of theories of light nicely demonstrates the ways in which theories are used as science ... show full transcript
Worked Solution & Example Answer:Read the following passage and answer the accompanying questions - Leaving Cert Physics - Question 11 - 2016
Step 1
State the laws of refraction.
Answer
The laws of refraction state:
- When light travels from one medium to another, it changes speed, which results in bending.
- The incident ray, refracted ray, and normal line at the point of incidence all lie in the same plane.
- Snell's Law can be expressed as: where ( n_1 ) and ( n_2 ) are the refractive indices of the respective media.
Step 2
Draw a ray diagram to show the formation of a virtual image in a magnifying glass.
Answer
To illustrate the formation of a virtual image in a magnifying glass:
- Draw the lens as a converging lens (convex).
- Position the object closer than the focal point of the lens.
- Use ray tracing:
- Draw an incident ray from the top of the object parallel to the principal axis.
- After refraction, it should pass through the focal point on the opposite side.
- Draw another ray going through the center of the lens which continues straight.
- The intersection of the rays should be behind the lens, indicating the position of the virtual image.
Step 3
Explain what is meant by the term wavelength.
Answer
Wavelength refers to the distance between two consecutive crests (or troughs) in a wave. It is a critical parameter in wave physics, typically denoted by the symbol ( \lambda ). The wavelength determines the color of visible light and is measured in meters (m).
Step 4
As part of his investigations into light, Newton dispersed light with a prism. List the colours observed by Newton, in order, starting with the colour that was refracted the least.
Answer
The colors observed by Newton, in order from least refracted to most refracted, are:
- Red
- Orange
- Yellow
- Green
- Blue
- Indigo
- Violet
Step 5
In Young’s experiment to demonstrate the wave nature of light he needed two coherent sources of light. How might he have produced these sources?
Answer
To produce two coherent light sources, Young may have used:
- Two slits in an opaque barrier, allowing light from a single source to pass through both slits creating two wavefronts that maintain a constant phase relationship.
- Two separate light bulbs that are connected to a single power source to keep them in phase with each other (often referred to as 'grating').
Step 6
Calculate the energy of a photon of green light, which has a wavelength of 510 nm.
Answer
The energy of a photon can be calculated using the formula:
Where:
- ( E ) is the energy of the photon,
- ( h = 6.63 \times 10^{-34} , J \cdot s ) (Planck's constant),
- ( c = 3 \times 10^8 , m/s ) (speed of light),
- ( \lambda = 510 , nm = 510 \times 10^{-9} , m ).
Substituting the values:
Step 7
Quantum mechanics is used to explain how electrons in atoms produce line emission spectra. Describe how these spectra are produced.
Answer
Line emission spectra are produced through the following steps:
- Electrons absorb energy to move to a higher energy level (excitation).
- When these excited electrons return to a lower energy level, they emit energy in the form of light or electromagnetic radiation.
- The specific wavelengths of light emitted correspond to the differences between energy levels, resulting in distinct lines in the spectrum.
Step 8