Crossword Genius

Disparaging viewpoint is when reflection takes over (8,5)

Ross

I believe the answer is:

critical angle

I'm a little stuck... Click here to teach me more about this clue!

'when reflection takes over' is the definition.
I can't tell whether this defines the answer.

'disparaging viewpoint' is the wordplay.
'disparaging' becomes 'critical' (I've seen this in another clue).
'viewpoint' becomes 'angle' (angle is a kind of viewpoint).
'critical'+'angle'='CRITICAL ANGLE'

'is' is the link.

Can you help me to learn more?

I've seen this clue in The Daily Express.
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