DP Physics Questionbank

The incident ray shown in the diagram makes a significant angle with the optical axis.

(i) State the aberration produced by these kind of rays.

(ii) Outline how this aberration is overcome.

Determine the distance between the lamp and the lens.

Calculate the focal length of the lens.

State what is meant by a virtual image.

Show that the image of the object formed by L₁ is 12 cm to the right of L₁.

The distance between the lenses is 18 cm. Determine the focal length of L₂.

On the diagram draw rays to locate the focal point of L₂. Label this point F.

On the diagram, sketch the part of wavefront X that is inside the lens.

On the diagram, sketch the wavefront in air that passes through point P. Label this wavefront Y.

Explain your sketch in (a)(i).

Two parallel rays are incident on a system consisting of a diverging lens of focal length 4.0 cm and a converging lens of focal length 12 cm.

The rays emerge parallel from the converging lens. Determine the distance between the two lenses.

Determine the position of the image.

Identify whether the image is real or virtual.

The lens is 18 cm from the screen and the image is 0.40 times smaller than the object. Calculate the power of the lens, in cm^–1. 

Light passing through this lens is subject to chromatic aberration. Discuss the effect that chromatic aberration has on the image formed on the screen.

A system consisting of a converging lens of focal length F₁ (lens 1) and a diverging lens (lens 2) are used to obtain the image of an object as shown on the scaled diagram. The focal length of lens 1 (F₁) is 30 cm.

Determine, using the ray diagram, the focal length of the diverging lens.

determine the focal length of the lens.

calculate the linear magnification.

The diagram shows an incomplete ray diagram which consists of a red ray of light and a blue ray of light which are incident on a converging glass lens. In this glass lens the refractive index for blue light is greater than the refractive index for red light.

Using the diagram, outline the phenomenon of chromatic aberration.

Identify, with the letter X, the position of the focus of the primary mirror.

Suggest how the refracted rays in (a) are modified when the converging lens is replaced by a diverging lens.

Hence state how the defect of the converging lens in (a) may be corrected.

Calculate the distance between the lenses.

Determine, by calculation, the linear magnification produced in the above diagram.

Construct a ray diagram in order to locate the position of the image formed by the mirror. Label the image $\text{I}$.

Estimate the linear magnification of the image.

Explain chromatic aberration, with reference to your diagram in (b)(i).

Calculate, in cm, the distance between the eyepiece and the image formed by the objective lens.

Draw on the diagram the three wavefronts after they have passed through the lens.

Lens A has a focal length of $4.00 \mathrm{cm}$. An object is placed $4.50 \mathrm{cm}$ to the left of A. Show by calculation that a screen should be placed about $0.4 \mathrm{m}$ from A to display a focused image.

The screen is removed and the image is used as the object for a second diverging lens B, to form a final image. Lens B has a focal length of $2.00 \mathrm{cm}$ and the final real image is $8.00 \mathrm{cm}$ from the lens. Calculate the distance between lens A and lens B.

Calculate the total magnification of the object by the lens combination.

A student has four converging lenses of focal length 5, 20, 150 and 500 mm. Determine the maximum magnification that can be obtained with a refracting telescope using two of the lenses.

There are optical telescopes which have diameters about 10 m. There are radio telescopes with single dishes of diameters at least 10 times greater.

(i) Discuss why, for the same number of incident photons per unit area, radio telescopes need to be much larger than optical telescopes.

(ii) Outline how is it possible for radio telescopes to achieve diameters of the order of a thousand kilometres.

The diagram shows a schematic view of a compound microscope with the focal points f_o of the objective lens and the focal points f_e of the eyepiece lens marked on the axis.

On the diagram, identify with an X, a suitable position for the image formed by the objective of the compound microscope.

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 7.8 × 10^–3 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.

Determine the focal length of each lens.

The telescope is used to form an image of the Moon. The angle subtended by the image of the Moon at the eyepiece is 0.16 rad. The distance to the Moon is 3.8 x 10⁸ m. Estimate the diameter of the Moon.

State two advantages of the use of satellite-borne telescopes compared to Earth-based telescopes.

When the Earth-Moon distance is 363 300 km, the Moon is observed using the telescope. The mean radius of the Moon is 1737 km. Determine the focal length of the mirror used in this telescope when the diameter of the Moon’s image formed by the main mirror is 1.20 cm.

This arrangement using the secondary mirror is said to increase the focal length of the primary mirror. State why this is an advantage.

Distinguish between this mounting and the Newtonian mounting.

It is proposed to build an array of radio telescopes such that the maximum distance between them is 3800 km. The array will operate at a wavelength of 2.1 cm.

Comment on whether it is possible to build an optical telescope operating at 580 nm that is to have the same resolution as the array.

Determine the magnification of the microscope.

The image at I is the object for a second converging lens. This second lens forms a final image at infinity with an overall angular magnification for the two lens arrangement of 5. Calculate the distance between the two converging lenses.

A new object is placed a few meters to the left of the original lens. The student adjusts spacing of the lenses to form a virtual image at infinity of the new object. Outline, without calculation, the required change to the lens separation.

Calculate, in cm, the distance between the eyepiece and the image formed by the objective lens.

Determine, in cm, the focal length of the objective lens.

Outline the meaning of normal adjustment for a compound microscope.

State the main physical difference between step-index and graded-index fibres.

State two advantages of optic fibres over coaxial cables for these transmissions.

Suggest why infrared radiation rather than visible light is used in these transmissions.

A signal with an input power of 15 mW is transmitted along an optic fibre which has an attenuation per unit length of 0.30 dB$$km^–1. The power at the receiver is 2.4 mW.

Calculate the length of the fibre.

State and explain why it is an advantage for the core of an optic fibre to be extremely thin.

The diagram shows a ray of light in air that enters the core of an optic fibre.

The ray makes an angle A with the normal at the air–core boundary. The refractive index of the core is 1.52 and that of the cladding is 1.48.

Determine the largest angle A for which the light ray will stay within the core of the fibre.

Identify the features of the output signal that indicate the presence of attenuation and dispersion.

The length of the optic fibre is 5.1 km. The input power of the signal is 320 mW. The output power is 77 mW. Calculate the attenuation per unit length of the fibre in dB$$km^–1.

Calculate the maximum angle β for light to travel through the fibre.

Refractive index of core       = 1.50
Refractive index of cladding = 1.48

Calculate the critical angle at the core−cladding boundary.

The use of optical fibres has led to a revolution in communications across the globe. Outline two advantages of optical fibres over electrical conductors for the purpose of data transfer.

Draw on the axes an output signal to illustrate the effect of waveguide dispersion.

Calculate the power of the output signal after the signal has travelled a distance of 3.40 km in the fibre.

Explain how the use of a graded-index fibre will improve the performance of this fibre optic system.

An optic fibre of refractive index 1.4475 is surrounded by air. The critical angle for the core – air boundary interface is 44°. Suggest, with a calculation, why the use of cladding with refractive index 1.4444 improves the performance of the optic fibre.

Calculate the maximum attenuation allowed for the signal.

An amplifier can increase the power of the signal by 12 dB. Determine the minimum number of amplifiers required.

The graph shows the variation with wavelength of the refractive index of the glass from which the optic fibre is made.

Two light rays enter the fibre at the same instant along the axes. Ray A has a wavelength of λ_A and ray B has a wavelength of λ_B. Discuss the effect that the difference in wavelength has on the rays as they pass along the fibre.

In many places clad optic fibres are replacing copper cables. State one example of how fibre optic technology has impacted society.

Calculate n.

Show that the longest path is 66 m longer than the shortest path.

Determine the time delay between the arrival of signals created by the extra distance in (b)(i).

Explain the shape of the signal you sketched in (b)(ii).

Determine the distance at which the signal must be amplified.