Stellar distances are measured in

Fill in the blanks: Steller distances are measured in __________.

In spherical lenses, all distance are measured from ___________.

In case of spherical mirrors, all distances are measured from………. .

All the distances are measured from the ………….. Of the lens.

State units of larger distances measured in astrononers.

State units of smaller distances measured.

Why could you not use an elastic measuring tape to measure distance ? What would be some of the problems you would meet in telling someone about a distance you measured with an elastic tape ?