An astronomical telescope is used in normal adjustment. The separation of the lenses in the telescope is 0.84 m. The objective lens has a focal length of 0.82 m.
Calculate the magnification of this telescope.
Outline why sign convention is necessary in optics.
A student decides to reverse the positions of the same lenses without changing the separation to form an optical microscope in normal adjustment. The student's near point is 0.25 m from her eye.
The diagram is a partially-completed ray diagram for a compound microscope that consists of two thin converging lenses. The objective lens L1 has a focal length of cm. The object is placed cm to the left of L1. The final virtual image is formed at the near point of the observer, a distance of cm from the eyepiece lens L2.
Two converging lenses are used to make an astronomical telescope. The focal length of the objective is cm and that of the eyepiece is cm. The telescope is used to form a final image of the Moon at infinity.
The diagram is a partially-completed ray diagram for a compound microscope that consists of two thin converging lenses. The objective lens L1 has a focal length of cm. The object is placed cm to the left of L1. The final virtual image is formed at the near point of the observer, a distance of cm from the eyepiece lens L2.
Two converging lenses are used to make an astronomical telescope. The focal length of the objective is cm and that of the eyepiece is cm. The telescope is used to form a final image of the Moon at infinity.
State what is meant by a virtual image.
Show that the image of the object formed by is 12 cm to the right of .
The distance between the lenses is 18 cm. Determine the focal length of L_{2}.
On the diagram draw rays to locate the focal point of L2. Label this point F.
Explain why, for the final image to form at infinity, the distance between the lenses must be 87.5 cm.
The angular diameter of the Moon at the naked eye is rad.
Calculate the angular diameter of the final image of the Moon.
By reference to chromatic aberration, explain one advantage of a reflecting telescope over a refracting telescope.
Explain the cause of the radio-frequency emissions from a patient's body during nuclear magnetic resonance (NMR) imaging.
Outline how a gradient field allows NMR to be used in medical resonance imaging.
Identify one advantage of NMR over ultrasound in medical situations.
This question is about medical imaging.
Outline the basis of computerized tomography (CT scanning).
State and explain one disadvantage of the use of computerized tomography.
This question is about the use of ultrasound.
Define acoustic impedance.
State the significance of acoustic impedance in the use of ultrasound techniques.
Medical practitioners select the frequency of the ultrasound depending on the diagnosis they are undertaking. Outline the importance of using ultrasound of the appropriate frequency.
A telescope can just resolve images that are separated by an angle of rad. Two stars are a distance of from each other.
What is the maximum distance between the stars and the telescope for their images to be resolved by the telescope?
This question is about charge-coupled devices (CCD).
With reference to a CCD, state what is meant by a pixel.
Outline how light falling on a CCD leads to an electrical signal being produced by a pixel.
State one other piece of information that needs to be collected, in addition to the electrical signal in , in order that an image may be formed.
Suggest two advantages of a CCD in comparison with a photographic film for image production.
This question is about determining the distance to a nearby star. Two photographs of the night sky are taken, one six months after the other. When the photographs are compared, one star appears to have shifted from position A to position B, relative to the other stars.
Outline why the star appears to have shifted from position A to position B.
The observed angular displacement of the star is θ and the diameter of the Earth's orbit is d. The distance from the Earth to the star is D. Draw a diagram showing d, D and θ.
Explain the relationship between d, D and θ.
One consistent set of units for D and θ are parsecs and arc-seconds. State one other consistent set of units for this pair of quantities.
Suggest whether the distance from Earth to this star can be determined using spectroscopic parallax.
This question is about nuclear and particle physics.
Draw a schematic diagram of one type of mass spectrometer.
Describe, using your diagram in , how the existence of isotopes may be determined.
Nucleons are made up of quarks and belong to a class of particles called hadrons. There is a strong interaction and also a weak interaction between quarks. State the name of the exchange particle associated with the strong interaction between quarks.
State the name of the exchange particle associated with the weak interaction between quarks.
State the name of the exchange particle associated with the strong interaction between hadrons.
This question is about optic fibres. An optic fibre consists of a thin glass fibre surrounded by a cladding material. The refractive index of the glass is 1.62.
Calculate the critical angle for this optic fibre.
The diagram shows a straight optic fibre. Sketch the passage of a ray of light through the fibre.
The input power to the fibre is 150 mW . The attenuation per unit length of the glass fibre is . When the light has travelled a distance its power has fallen to 3.00 mW , at which point amplification of the signal is required. Determine .
The variation with time of the input power to an optic fibre of length is shown in diagram 1. The variation with time of the output power from the optic fibre is shown in diagram 2. The output power in diagram 2 is not to the same scale as the input power on diagram 1.
The output power is much smaller than the input power because energy is absorbed as the light passes along the optic fibre.
One difference between the shape of the input and output signals is that the output signal is noisier than the input signal. State and explain one other difference between the shape of the input signal and the output signal.
Describe how the output signal can be restored to its original shape.