S3 Phy

Which of the following shows the light rays of a sun on earth?

• Convergent rays

• Parallel rays

• Divergent rays

• Unable to determine

Which of the followings is/are correct concerning laws of reflection?

• Reflection only occurs in mirrors

• The incident ray, reflected ray and the normal all lie on the same plane.

• The angle of reflection r is always equal to the angle of incidence i. (i=r)

• The Snell's law can be expressed as $\frac{\sin\theta_a}{\sin\theta_x}$ when there is air in the process, while a represents air and x represents the object.

The reflection on smooth surfaces such that the parallel rays reflected are in the same direction is called ____ reflection.

The reflection on rough surfaces such that the reflected parallel rays are reflected towards different directions is called ____ reflection.

The image formed by a plane mirror is

• Virtual

• At the same distance from the mirror as the object is (image distance = object distance)

• Of the same size as the object

• Erect but laterally inverted

• All of the above

John is 1.8m tall and his eyes are 0.1m lower, he is looking into a mirror.

What is the minimum length of the mirror in order to reflect his whole body

Note: The distance between the person and the plane mirror is not considered.

• 1.8m

• 0.9m

• 0.85m

• He can see himself at whatever length of the mirror.

May is 1.5m tall and her eyes are 0.1m lower, she is looking into a mirror.

It is known that the length of the mirror is 0.75m long, How high up from the ground should the lower end of the mirror be in order to reflect her whole body?

Note: The distance between the person and the plane mirror is not considered.

• $\frac{1.5\left(height\right)}{2}=0.75m$

• $1.5\left(height\right)-0.1\left(eye\ level\right)=1.4m$

• $\frac{1.5\left(height\right)-0.1\left(eye\ level\right)}{2}=0.7m$

• It cannot be determined

Which of the followings concerning Snell's Law is/are correct?

• The original equation is  $n_1\sin\theta_1=n_2\sin\theta_2$ .

•  $n_x=\frac{\sin\theta_y}{\sin\theta_x}$  is correct while x and y are not air.

• The calculation of a refractive index travelling from air to medium x is $n_x=\frac{\sin\theta_a}{\sin\theta_x}$  because the refractive index of air is approximately 1.

• The original equation is $n_x=\frac{c}{v}$  .

Which of the followings concerning laws of refraction is/are correct?

• $\frac{\sin\theta_a}{\sin\theta_g}$ is equal to constant (refractive index of g), such that $\sin\theta_a$ is proprtional to $\sin\theta_g$ .

• The light ray bends away from the normal when it travels from an optically less dense medium to an optically denser medium.

• $n_g=\frac{c}{v}$

• The incident ray, refracted ray and normal all lie on the same plane.

The light ray bends ____ the normal when it travels from an optically denser medium and bends ____ when it travels to an optically denser medium.

• away from, towards

• towards, away fro,

• away from, away from

• straight from, straight from