AQA · A level Physics

Euclid quasar redshift A-level Physics challenge

Can you get 100%? Use Euclid's ancient quasars to test redshift, observed wavelength, infrared astronomy and black-hole evidence.

Read how Euclid finds ancient quasars

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Question

8 marks

Answer all parts. Show your working and give units where appropriate.

1(a)

A hydrogen spectral feature is emitted at wavelength 121.6 nm. A quasar has redshift

z = 7.77, w h er e 1 + z = o b ser v e d w a v e l e n g t h / e mi tt e d w a v e l e n g t h

. Calculate the observed wavelength in micrometres.

[3 marks]

1(b)

Explain why an infrared-sensitive telescope is useful for finding quasars whose strongest emitted features were originally ultraviolet.

[2 marks]

1(c)

A quasar is powered by matter falling towards a supermassive black hole. Explain why detecting many luminous quasars at very high redshift constrains models of early black-hole growth, and state one important selection effect.

[3 marks]

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