Option 1 states that the longest wavelength of light visible to the human eye is about 700 nm. This statement is correct. The human eye can perceive different wavelengths of light within a specific range, known as the visible spectrum. The longest wavelength in this range appears as red light, which has a wavelength around 700 nm.

Option 2 states that the shortest wavelength of light visible to the human eye is about 400 nm. This statement is also correct. The shortest wavelength in the visible spectrum appears as violet light, which has a wavelength around 400 nm.

Option 3 states that the wavelength of gamma rays is longer than that of X-rays. This statement is not correct. In reality, gamma rays have shorter wavelengths than X-rays. Gamma rays are a form of electromagnetic radiation with the shortest wavelengths in the electromagnetic spectrum. X-rays have longer wavelengths than gamma rays but shorter wavelengths than ultraviolet light.

Option 4 states that the ability of a telescope to form separate images of close objects is called its resolving power. This statement is correct. Resolving power refers to the ability of a telescope or other optical instrument to distinguish between closely spaced objects or details. Higher resolving power allows for clearer and sharper images of objects that are close together.