Most Repeated MDCAT Physics: Optics, Nature of Light and Optical Instruments MCQs

Explanation

This is the correct answer. To form an erect image twice as large as the object using a convex lens, the object must be placed between the focal point and the optical center of the lens. Focal length (f): 20 cm Magnification (m): 2 (since the image is twice as large as the object)Using the lens formula:1/v - 1/u = 1/fWhere: v is the image distance u is the object distanceSince the magnification is positive for an erect image:m = v/u = 2Therefore: v = 2uSubstituting this into the lens formula: 1/(2u) - 1/u = 1/20 cm Solving for u:u = 10 cmTherefore, the object must be placed 10 cm from the lens to form an erect image twice as large as the object.

Explanation

We can find focus coordinate from mirror equation: 1/u + 1/v = 1/f as the image is virtual, v is negative. And we find: 1/f = 1/60 - 1/20 = -2/60 = - 1/30 Hence, the focus is at 30 cm from the mirror. Focus and radius of curvature are connected as: R= 2f = 60 cm.

Explanation

Statement I is correct because a concave lens is diverging.Statement II is incorrect because the refracted rays will not be parallel to the principal axis.Statement III is incorrect because this is not true.Statement IV is incorrect because a concave lens is diverging while a convex lens is converging. Judging from our deductions about the statements, none of the options A, B, C, or D are correct. Hence option E is the right answer.

Explanation

For an object placed at twice the focal length of a convex lens, the image will be inverted, real, and the same size. So the correct answer here should be E. This can be confirmed using a ray diagram.

Explanation

The object is placed 10 cm from a converging lens with a focal length of 20 cm, meaning it is inside the focal point. For converging lenses, when the object is placed between the focal point and the lens, the image formed is virtual and erect. Thus, the correct answer is 'Both Virtual and Erect'.Options stating the image is real or simply erect without being virtual are incorrect because a real image would be inverted, and a solely erect image implies it must also be virtual.

Explanation

Incident rays of light parallel to the principal axis of the convex lens converge at the principal focus.A convex lens also known as a converging lens is thick in the middle and thin at the edges. It converges the light rays coming from a source on the principal focus. A principle focus of a convex lens is defined as the point on the principal axis on which the light rays coming parallel to the principal axis converge after getting refracted from the convex lens.

Explanation

Diffraction is the slight bending of light as it passes around the edge of an object. The amount of bending depends on the relative size of the wavelength of light to the size of the opening.

Explanation

By using c = f λ f = c/λ = 3 ×10^8/3 × 10^-7 f = 1 × 10^8+7 f = 1 × 10^15 Hz Hence, option c is correct.

Explanation

As E = hf Where, h is constant. Energy is determined by frequency. Hence, option A is correct.

Explanation

Transverse waves which include all electromagnetic waves such as light, radio waves, and x-rays can be polarized, hence the answer will be C.

Explanation

When a soap bubble is charged, either positively or negatively, the like charges spread over its surface due to electrostatic forces. These like charges repel each other, causing the bubble to expand and increase in size. Option B is correct because it accurately describes this phenomenon. Options A and C are incorrect as they suggest a decrease or no change in size, which contradicts the effects of electrostatic repulsion. Option D is incorrect because there is indeed a change.

Explanation

"Ultrasound" waves are longitudinal in nature, hence they cannot be polarized.Only transverse waves like electromagnetic waves can be polarized.

Explanation

Photon velocity equals the speed of light. Photons are massless, but they have energy E = hf = hc/λ. Here h = 6.626*10-34 Js is called Planck's constant. The photon energy is inversely proportional to the wavelength of the electromagnetic wave.E=6.626×10−34 × 3×108​/1240×10-9 ≈ 1.00 eV.

Explanation

Diffraction, the spreading of waves around obstacles.Diffraction is the slight bending of light as it passes around the edge of an object. The amount of bending depends on the relative size of the wavelength of light to the size of the opening.So the correct option is A.

Explanation

The magnifying power or angular magnification is defined as the ratio of the angles subtended by the image as seen through the optical device to that subtended by the object at the unaided eye.