ECAT MCQs

An object at 2f forms an image at 2f.
The mirror equation gives v=20 cm.

Refractive index generally depends on wavelength.
A prism therefore bends colors by different amounts.

Use f=c/λ with λ=600×10^-9 m.
F=3×10^8/(6×10^-7)=5×10^14 Hz.

Diffraction becomes pronounced when dimensions are comparable to wavelength.
It limits optical resolution.

Electric charge occurs in positive and negative forms.
Like charges repel and unlike charges attract.

The law of reflection gives equal incidence and reflection angles.
Both are measured from the normal.

Coulomb's law describes electrostatic force between point charges.
The force acts along the line joining the charges.

A plane mirror forms the image the same distance behind as the object is in front.
Therefore the object distance is 2 m.

Electric field is a vector quantity E=F/q.
Its direction is the force direction on a positive test charge.

Refractive index is n=c/v.
N=3.0×10^8 / 2.0×10^8 = 1.5.

Electric potential is a scalar measured in volts.
Potential difference drives charge movement in circuits.

Use v=c/n.
V=3.0×10^8/1.25 = 2.4×10^8 m/s.