Answer: f = -12 cm
Explanation: <u>Combined</u> <u>lenses</u> is an array of simple lenses with a common axis. The combination is useful for correction of optical aberrations which cannot be corrected by simple lenses.
When two lenses are in contact and are thin, focal lengths are related as:

If there is a distance between the lenses, the focal length will be:

Since the lenses in the question above are thin and in contact, the focal length of one of them will be:




-12
The focal length of the other lens is -12 cm, with the negative sign meaning it's a converging lens.
Answer:
Rate at which current flows is measured in amperes
Explanation:
The rate of flow of electrons constitutes the current. The electrons flow from lower electric potential to higher electric potential. When there is no potential difference then no electron will flow. The direction of the current and the electron are in opposite direction.
The direction of electron from the negative terminal to the positive terminal. The direction of current is from the positive terminal to the negative terminal.The current is measured in ampere.
The expression for current and the charge is as;
Here, q is the charge, t is the time taken and I is the current.
According to the given problem, Jodi made a list about electric current to help her study for a test. He described that electrons move from areas of low to high electric potential, voltage causes current to flow and movement of electrons is continuous in a current.
But he did error. It should be "rate at which charges flow" instead of rate at which current flow.
Therefore, the option (4) is correct.
the car travels 34 mi in one hour.
then, in 6 hours car travels
34 x 6 mi
= 204 mi