For analyzing optical problems involving the eye, what quantity is fixed (for seeing something in focus)?

The distance of the image is fixed.

Explanation:

Eye diseases like macular degeneration, glaucoma, and cataracts, can cause problem in seeing properly. Symptoms change in huge amount among these problems, so keep up with your eye exams. Some change in the seeing power can be hazardous and need immediate medical care.

For detecting the particular problem in the vision or the problem your eye is going through, the thing that is to be kept fixed and not changed at all is the distance at which an image is kept which is to be focused at to see the problem.

answer: the exterior temperature of commercial jet planes as they leave the stratosphere and return to the ground increases steadily.

explanation:

the lower most layer of atmosphere is troposphere which extends from 0 to 12 km above the surface of the earth. the temperature initially decreases as distance is increased from the earth's surface. commercial jets fly in lower part of the stratosphere. the stratosphere extends upto 50 km. the temperature in stratosphere starts rising again due to presence of ozone which traps the uv rays.

thus, when the planes leave the stratosphere and return to the ground, the exterior temperature increases steadily.

5 w for 1hr = 5x60x60 joules=300x60=3000x6=18,000j as total energy conversion. efficiency of bulb needed for radiant to thermal within 18000