A concave objective lens and a convex eyepiece lens a convex objective lens and a concave eyepiece lens concave objective and eyepiece lenses convex objective and eyepiece lenses

i believe the answer is a

okay i have so many questions. but the big one here is: um wt..f is this mess? ?

adding a(n) to an electric circuit would increase the magnetic field around a wire;

b. solenoid

a solenoid is a type of electromagnet whose purpose is to generate a controlled magnetic field.

if the purpose of the solenoid is instead to impede changes in the electric current, a solenoid can be more specifically classified as an inductor rather than an electromagnet.

force required to detach it is given by

charges are taken to be fundamental charge

now we have

so above is the minimum distance at which it will detach