Ask how this light ray got to that point on the mirror. If it came from the candle, the angles will not be equal. Draw the light ray so that the angles are equal. It will be seen that this light ray came from the other mirror. It got to that mirror from the object candle, making equal angles at that first mirror, reflecting to the second mirror and then out.
Light reflects making equal angles.
The colleges were closed to reduce the chance of spreading the disease through the student population. Isaac Newton spent the next 18 months experimenting with light and researching his observations in Latin.