DH reread CH 30

[Zara]

No: HPFGUIDX 187464

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> "Professor McGonagall moved faster than Harry could have believed: her wand slashed through the air and for a split second Harry thought that Snape must crumble, unconscious, but the swiftness of his Shield Charm was such that McGonagall was thrown off balance" - p.481, brit.ed.
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> Alla:
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> How does Harry know what Minerva is casting here? That he expects that Snape must crumble, unconscious? Is it just due to what sort of wand movements he sees (slashing equals attack?) or something else?

Zara:
Several spells have been described in the books as looking like bolts or jets of variously colored light. I presume Minerva chose to case the Stunning Spell, Stupefy, which appears as a red bolt of light. Severus's chosen defense, a Shield Charm, would not prevent Minerva's spell from shooting across the hall in his direction, it would merely deflect it harmlessly, so that Harry could see what she was casting from the color. This would also be consistent with his expectation that Severus would be rendered unconscious, as that is what Stupefy does.