Monochromatic light is incident on the double-slits and the distance from the screen is 0.64 m. The distance between the bright fringes is 9.3 × 10–4 m. Determine the wavelength of the incident light.
If the wavelength of the incident light is halved and the distance between the slits is doubled, outline the effect on the separation of the fringes of the interference pattern.
Beam B is incident at the same end of the fibre. It refracts through the air-core boundary and then refracts again when it hits the core-cladding boundary at an angle of 51.8°, traveling along the boundary.
A different step-index optical fibre is built with the same core as that in part (a) but with a different material used for the cladding.
The speed of light in the new cladding material is 1.54 × 108 m s−1.
(d)
Explain why this new cladding material would not be suitable for sending signals through the step-index optical fibre. Use a calculation to support your answer.
A laboratory ultrasound transmitter emits ultrasonic waves of wavelength 0.7 cm through two slits. A receiver, moving along line AB, parallel to the line of the slits, detects regular rises and falls in the strength of the signal.
A student measures a distance of 0.39 m between the first and the fourth maxima in the signal when the receiver is 1.5 m from the slits.
The ultrasound transmitter is a coherent source.
(a)
Explain what is meant by the term coherent source.
Blue light from a laser is now passed through a single narrow slit. A pattern of bright and dark regions can be observed on the screen which is placed several meters beyond the slit.
(b)
Describe the effect on the diffraction pattern if the width of the narrow slit is decreased.
With the original slit width, state and explain the effect on the width of the fringes on the diffraction pattern if the blue light is replaced with a red light of the same intensity.
