HARD
9th CBSE
IMPORTANT
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The figure below is a schematic diagram of a reflecting telescope to view distant stars and constellations. OP is the imaginary axis of the eyepiece and light rays from the distant stars falling in parallel with OP.  The angle between the incident and reflected rays on the objective mirror is 25° and that on the secondary mirror is 35°.

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The angle subtended by light rays at the eyepiece APB is  °

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Important Questions on Lines and Angles

HARD
9th CBSE
IMPORTANT

The figure below is a dish antenna which has signal receiver placed at the focus, F. The centre of curvature of the antenna is C, and P is the point on the antenna on the same line joining C and F. The incoming signals after reflection (The angle of incidence is equal to the angle of reflection), passes through F, where signal receive is placed.

A signal travelling parallel to axis, CP makes an angle of incidence 25° LMC

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The measure of PFM is _____ °

 

HARD
9th CBSE
IMPORTANT

Two mirrors AC and AB are kept an angle 50° with each other. A ray of light falling on AB in parallel to AC suffers reflection at AB and then at AC.

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The angle of reflection at mirror AC (marked y in the figure) is _____ °

HARD
9th CBSE
IMPORTANT

Rohan made a shape using matchsticks as shown below, by attaching two legs at the opposite vertices of the square. The angle made by each leg with respect to side of the square is 65°.  Now Rohan wants to turn the matchstick on the right side so that it is parallel to the one on the left side.

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The angle by which Rohan should turn the matchstick on the right side is _____ °.

HARD
9th CBSE
IMPORTANT

The figure below shows front view of a solar panel fixed on a support, one end of which is firmly grounded at angle of 35° and other end is joined with solar panel using a rotatable hinge. The solar panel is fully raised by rotating by the required angle about the hinge on the support so that light rays falls perpendicular on the panel, at a time when sun is 20° vertical with the ground.

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The measure of angle between the support and solar panel once it is fully raised is _____ °

HARD
9th CBSE
IMPORTANT

Sita cutout three triangles of different types from a parallelogram ABCD for the purpose of classifying them. ADE is an isosceles triangle, AEC is an obtuse triangle, ABC is an acute triangle. Measure of two angles are marked in the figure.

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The measure of angle CAE is _____ °

HARD
9th CBSE
IMPORTANT

In the figure below J is meeting junction of three straight roads, R1, R2, R3. A car upon reaching junction J, the car turned right and entered into road R3.

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By what angle did the car turn at junction J?

HARD
9th CBSE
IMPORTANT

Below is the picture of Incheon Bridge, New Songdo City, South Korea, designed using cables. The angles between the vertical pole QT with each cable are equal PQT=RQT. The sum of angles each cable making with road is70° PQU+RQS=70°

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What is the angle that the cable PQ is making with the road, QU?

HARD
9th CBSE
IMPORTANT

The picture below is a road around a park, where the roads ACBD. CAD=50° and CBD=30°

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A person entering into road BD from road AD. By what angle should the person turn at D?