If I put a lamp in front of a mirror will I double the light?

The simple answer is no. The total amount of light produced is unchanged. However, the distribution of the light is altered and immediately in front of the lamp the light level will be roughly doubled.
Professor Colin Davidson, Tigh-nan-Eilean, Ardfern, Argyll

May I suggest the writer places a lamp between two facing mirrors and if he is incinerated the answer is probably yes.
John Forshaw, Bournemouth

Placing a mirror behind a light source will not enhance the total amount of light energy produced. However, it will increase the light intensity in a particular direction at the expense of the light intensity in other directions. This principle is used in torches, car headlights, searchlights and any other device that emits a beam of light.
Martin Vlietstra, Hampshire

Light is a variety of electromagnetic radiation in the form of particles called photons, which can also behave as waves. Luminosity of a source of light or an object depends on the number of light particles emanating from the source or striking the object.

The luminosity will be certainly increased if a lamp is placed in front of a mirror. A common example is the flashing light of police cars where mirrors revolve around a static lamp, thereby producing both a strobe effect and increased brightness of the light.
Sam Banik, London N10

From the cliffs above Dover I can often see France clearly. On other occasions on a bright day with a clear blue sky all I see is a sharp horizon but no France. How can this be?

Obviously the Sun has warmed up the Channel, which has expanded and pushed Europe away from the UK, making it invisible.
David Fellows, East Sussex

Refraction, or put simply a mirage, is the answer. Light is refracted at varying amounts depending on the atmospheric conditions. This is the same as seeing an oasis on the horizon while walking through the desert only to find it is farther than you expected or would even disappear the next day (because of a change in temperature or humidity).

Interestingly, I witnessed this phenomenon in the Antarctic while working for the British Antarctic Survey on the Brunt ice shelf. Although we were some distance from the sea, we could clearly see icebergs, sometimes even floating above the horizon!
Richard Lambert, Wantage, Oxon

How do woodpeckers avoid concussing themselves when they obsessively hammer away at tree trunks?

Further to Christopher Gardner-Thorpe’s response (May 23, 2008), I had just finished whitewashing a whole wall on a Mid-Wales cottage a few years ago and stepped back to admire my handiwork when a startled green woodpecker flew straight out of the wood and into the wall at full speed. It fell lifeless to the ground. I reasoned sadly at the time that although it had developed the ability to cope with the forces involved in pecking at right angles to its spine, a blow along the line of the spine could still cause fatal injuries.

Might there be parallels with aggressive, head-butting behaviour in human beings?
Malcolm Burns, Leamington Spa

Why do princes William and Harry use their father’s title as a surname, instead of Windsor?
David Hepper, Woodbridge, Suffolk

Why is the waiting room at a radio or television studio usually referred to as the green room?
Philip Arkell, Winchcombe, Glos

We were taught at school that hot air rises. So why does it get cooler as you go up a mountain?
David Lee, Leigh-on-Sea, Essex

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