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Read the following passage and answer the accompanying questions - Leaving Cert Physics - Question 11 - 2018
Question 11
Read the following passage and answer the accompanying questions. The Irish Low Frequency Array, or I-LOFAR, is part of a €150 million network of radio telescope st... show full transcript
Worked Solution & Example Answer:Read the following passage and answer the accompanying questions - Leaving Cert Physics - Question 11 - 2018
Step 1
Calculate the minimum frequency of the radio waves detected by I-LOFAR.
Answer
Given that the wavelength, ( \lambda = 30 \text{ m} ), we can use the formula: [ f = \frac{v}{\lambda} ] Assuming the speed of radio waves in a vacuum is approximately ( v = 3 \times 10^8 \text{ m/s} ), we can calculate: [ f = \frac{3 \times 10^8 \text{ m/s}}{30 \text{ m}} = 1 \times 10^7 \text{ Hz} ]
Step 2
Draw a diagram of the magnetic field around the Earth.
Answer
The diagram should illustrate the magnetic field lines around the Earth:
- The Earth is represented as a circle.
- Magnetic field lines extend outward from the poles.
- The direction should indicate from the South pole to the North pole and curve around the Earth.
Step 3
Explain how information is transmitted using optical fibres.
Answer
Information is transmitted through optical fibres by means of light signals. The key points are:
- Light travels through the fibre and undergoes total internal reflection.
- Data is encoded in light by modulating its intensity, frequency, or phase.
- Optical fibres have a core with a higher refractive index than the cladding, ensuring that light is contained within the core.
Step 4
Calculate the position of the image of a person standing 75 cm from the Leviathan mirror.
Answer
Using the mirror formula: [ \frac{1}{f} = \frac{1}{v} + \frac{1}{u} ] where ( u = -75 \text{ cm} ) (real object) and ( f = 16 \text{ m} = 1600 \text{ cm} ) [ \frac{1}{1600} = \frac{1}{v} - \frac{1}{75} ] Solving this will give: [ v \approx 79 \text{ cm} ]
Step 5
Where, with respect to the concave mirror, will an image of the moon be formed? Justify your answer.
Answer
The image of the moon will form:
- At its focal point, since the moon is far enough away, incoming rays can be considered parallel due to its distance.
- Justification: For a concave mirror, parallel rays converge at the focal point.
Step 6
A concave mirror can also be used as a microscope to magnify images. Draw a ray diagram to show the formation of an upright, magnified image in a concave mirror.
Answer
The ray diagram should include:
- Concave mirror showing curvature.
- Object placed between the focal point and the mirror.
- Two rays, one parallel to the principal axis reflecting through the focal point, and another passing through the focal point reflecting parallel to the axis.
- The image is formed upright and magnified on the same side as the object.
Step 7
Calculate the velocity of the Hubble telescope as it orbits the Earth.
Answer
Using the formula for the orbital velocity: [ v = \frac{2 \pi r}{T} ] Where:
- ( r = 6400 \text{ km} + 570 \text{ km} = 6970 \text{ km} = 6.97 \times 10^6 \text{ m} )
- ( T = 15.1 \text{ orbits/day} ) (convert to seconds) Calculating this gives: [ v \approx 7650 ext{ m/s} ]
Step 8
Name one optical phenomenon which reduced the effectiveness of the Leviathan and which is eliminated by the location of the Hubble telescope. How does the location of the Hubble telescope eliminate this problem?
Answer
The optical phenomenon is refraction. Hubble is above the atmosphere, which eliminates the effects of atmospheric distortion, allowing for clearer images than those captured by ground-based telescopes like the Leviathan.